Update webview doc

Summary:
Reference: facebook#8203

Changes made:

Added a webview example to the intro section
Added more details to prop explanations
Test plan (required)

Ran the website locally and checked: http://localhost:8079/react-native/docs/webview.html

![component_webview_2](https://cloud.githubusercontent.com/assets/691109/16316552/f6847c56-393b-11e6-8fdd-a0b61e7f787b.png)
Closes facebook#8372

Differential Revision: D3477685

Pulled By: JoelMarcey

fbshipit-source-id: a624f5c6c12a8367aea2a6e7c2e520da7a074bbd

Author: Christine Abernathy

Libraries/Components/WebView/WebView.ios.js

@@ -82,7 +82,26 @@ var defaultRenderError = (errorDomain, errorCode, errorDesc) => (
 );
 
 /**
- * Renders a native WebView.
+ * `WebView` renders web content in a native view.
+ *
+ *```
+ * import React, { Component } from 'react';
+ * import { WebView } from 'react-native';
+ *
+ * class MyWeb extends Component {
+ *   render() {
+ *     return (
+ *       <WebView
+ *         source={{uri: 'https://github.com/facebook/react-native'}}
+ *         style={{marginTop: 20}}
+ *       />
+ *     );
+ *   }
+ * }
+ *```
+ *
+ * You can use this component to navigate back and forth in the web view's
+ * history and configure various properties for the web content.
  */
 var WebView = React.createClass({
   statics: {
@@ -109,7 +128,7 @@ var WebView = React.createClass({
     source: PropTypes.oneOfType([
       PropTypes.shape({
         /*
-         * The URI to load in the WebView. Can be a local or remote file.
+         * The URI to load in the `WebView`. Can be a local or remote file.
          */
         uri: PropTypes.string,
         /*
@@ -155,96 +174,125 @@ var WebView = React.createClass({
      */
     renderLoading: PropTypes.func,
     /**
-     * Invoked when load finish
+     * Function that is invoked when the `WebView` has finished loading.
      */
     onLoad: PropTypes.func,
     /**
-     * Invoked when load either succeeds or fails
+     * Function that is invoked when the `WebView` load succeeds or fails.
      */
     onLoadEnd: PropTypes.func,
     /**
-     * Invoked on load start
+     * Function that is invoked when the `WebView` starts loading.
      */
     onLoadStart: PropTypes.func,
     /**
-     * Invoked when load fails
+     * Function that is invoked when the `WebView` load fails.
      */
     onError: PropTypes.func,
     /**
+     * Boolean value that determines whether the web view bounces
+     * when it reaches the edge of the content. The default value is `true`.
      * @platform ios
      */
     bounces: PropTypes.bool,
     /**
      * A floating-point number that determines how quickly the scroll view
-     * decelerates after the user lifts their finger. You may also use string
-     * shortcuts `"normal"` and `"fast"` which match the underlying iOS settings
-     * for `UIScrollViewDecelerationRateNormal` and
-     * `UIScrollViewDecelerationRateFast` respectively.
+     * decelerates after the user lifts their finger. You may also use the
+     * string shortcuts `"normal"` and `"fast"` which match the underlying iOS
+     * settings for `UIScrollViewDecelerationRateNormal` and
+     * `UIScrollViewDecelerationRateFast` respectively:
+     *
      *   - normal: 0.998
-     *   - fast: 0.99 (the default for iOS WebView)
+     *   - fast: 0.99 (the default for iOS web view)
      * @platform ios
      */
     decelerationRate: ScrollView.propTypes.decelerationRate,
     /**
+     * Boolean value that determines whether scrolling is enabled in the
+     * `WebView`. The default value is `true`.
      * @platform ios
      */
     scrollEnabled: PropTypes.bool,
+    /**
+     * Controls whether to adjust the content inset for web views that are
+     * placed behind a navigation bar, tab bar, or toolbar. The default value
+     * is `true`.
+     */
     automaticallyAdjustContentInsets: PropTypes.bool,
+    /**
+     * The amount by which the web view content is inset from the edges of
+     * the scroll view. Defaults to {top: 0, left: 0, bottom: 0, right: 0}.
+     */
     contentInset: EdgeInsetsPropType,
+    /**
+     * Function that is invoked when the `WebView` loading starts or ends.
+     */
     onNavigationStateChange: PropTypes.func,
-    startInLoadingState: PropTypes.bool, // force WebView to show loadingView on first load
+    /**
+     * Boolean value that forces the `WebView` to show the loading view
+     * on the first load.
+     */
+    startInLoadingState: PropTypes.bool,
+    /**
+     * The style to apply to the `WebView`.
+     */
     style: View.propTypes.style,
 
     /**
-     * Used on Android only, JS is enabled by default for WebView on iOS
+     * Boolean value to enable JavaScript in the `WebView`. Used on Android only
+     * as JavaScript is enabled by default on iOS. The default value is `true`.
      * @platform android
      */
     javaScriptEnabled: PropTypes.bool,
 
     /**
-     * Used on Android only, controls whether DOM Storage is enabled or not
+     * Boolean value to control whether DOM Storage is enabled. Used only in
+     * Android.
      * @platform android
      */
     domStorageEnabled: PropTypes.bool,
 
     /**
-     * Sets the JS to be injected when the webpage loads.
+     * Set this to provide JavaScript that will be injected into the web page
+     * when the view loads.
      */
     injectedJavaScript: PropTypes.string,
 
     /**
-     * Sets the user-agent for this WebView. The user-agent can also be set in native using
-     * WebViewConfig. This prop will overwrite that config.
+     * Sets the user-agent for the `WebView`.
      * @platform android
      */
     userAgent: PropTypes.string,
 
     /**
-     * Sets whether the webpage scales to fit the view and the user can change the scale.
+     * Boolean that controls whether the web content is scaled to fit
+     * the view and enables the user to change the scale. The default value
+     * is `true`.
      */
     scalesPageToFit: PropTypes.bool,
 
     /**
-     * Allows custom handling of any webview requests by a JS handler. Return true
-     * or false from this method to continue loading the request.
+     * Function that allows custom handling of any web view requests. Return
+     * `true` from the function to continue loading the request and `false`
+     * to stop loading.
      * @platform ios
      */
     onShouldStartLoadWithRequest: PropTypes.func,
 
     /**
-     * Determines whether HTML5 videos play inline or use the native full-screen
-     * controller.
-     * default value `false`
-     * **NOTE** : "In order for video to play inline, not only does this
-     * property need to be set to true, but the video element in the HTML
-     * document must also include the webkit-playsinline attribute."
+     * Boolean that determines whether HTML5 videos play inline or use the
+     * native full-screen controller. The default value is `false`.
+     *
+     * **NOTE** : In order for video to play inline, not only does this
+     * property need to be set to `true`, but the video element in the HTML
+     * document must also include the `webkit-playsinline` attribute.
      * @platform ios
      */
     allowsInlineMediaPlayback: PropTypes.bool,
 
     /**
-     * Determines whether HTML5 audio & videos require the user to tap before they can
-     * start playing. The default value is `false`.
+     * Boolean that determines whether HTML5 audio and video requires the user
+     * to tap them before they start playing. The default value is `false`.
      */
     mediaPlaybackRequiresUserAction: PropTypes.bool,
   },
@@ -337,7 +385,7 @@ var WebView = React.createClass({
   },
 
   /**
-   * Go forward one page in the webview's history.
+   * Go forward one page in the web view's history.
    */
   goForward: function() {
     UIManager.dispatchViewManagerCommand(
@@ -348,7 +396,7 @@ var WebView = React.createClass({
   },
 
   /**
-   * Go back one page in the webview's history.
+   * Go back one page in the web view's history.
    */
   goBack: function() {
     UIManager.dispatchViewManagerCommand(
@@ -370,6 +418,9 @@ var WebView = React.createClass({
     );
   },
 
+  /**
+   * Stop loading the current page.
+   */
   stopLoading: function() {
     UIManager.dispatchViewManagerCommand(
       this.getWebViewHandle(),
@@ -389,7 +440,7 @@ var WebView = React.createClass({
   },
 
   /**
-   * Returns the native webview node.
+   * Returns the native `WebView` node.
    */
   getWebViewHandle: function(): any {
     return ReactNative.findNodeHandle(this.refs[RCT_WEBVIEW_REF]);