fix: allow to turn off prefetching globally

Author: egoist

README.md

@@ -73,6 +73,14 @@ new VueRouter({
 })
 ```
 
+It's also possible to turn of prefetching globally:
+
+```js
+Vue.use(RouterPrefetch, {
+  prefetch: false
+})
+```
+
 ### prefetchFiles
 
 - Type: `string[]`

src/index.js

@@ -1,7 +1,10 @@
 import prefetch from './prefetch'
 import { canPrefetch, supportIntersectionObserver, inBrowser } from './utils'
 
-function installRouterPrefetch(Vue, { componentName = 'RouterLink' } = {}) {
+function installRouterPrefetch(
+  Vue,
+  { componentName = 'RouterLink', prefetch: enablePrefetch = true } = {}
+) {
   const observer =
     supportIntersectionObserver &&
     new window.IntersectionObserver(entries => {
@@ -40,7 +43,7 @@ function installRouterPrefetch(Vue, { componentName = 'RouterLink' } = {}) {
     props: {
       prefetch: {
         type: Boolean,
-        default: true
+        default: enablePrefetch
       },
       prefetchFiles: {
         type: Array