Add ToggleSwitch component

.changeset/stupid-carrots-jam.md

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+---
+'@primer/react': minor
+---
+
+Adds a toggle switch component

docs/content/Switch.mdx

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+---
+componentId: switch
+title: Switch
+description: Toggles a setting on or off, and immediately saves the change
+status: Alpha
+source: https://github.com/primer/react/blob/main/src/Switch.tsx
+storybook: '/react/storybook?path=/story/switch-examples--default'
+---
+
+## Examples
+
+### Basic
+
+```jsx live
+<Box display="flex" maxWidth="300px">
+  <Box flexGrow={1} fontSize={2} fontWeight="bold" id="switchLabel">
+    Notifications
+  </Box>
+  <Switch aria-labelledby="switchLabel" />
+</Box>
+```
+
+### Uncontrolled (on)
+
+```jsx live
+<Box display="flex" maxWidth="300px">
+  <Box flexGrow={1} fontSize={2} fontWeight="bold" id="switchLabel">
+    Notifications
+  </Box>
+  <Switch defaultOn aria-labelledby="switchLabel" />
+</Box>
+```
+
+### Controlled
+
+```javascript noinline live
+const Controlled = () => {
+  const [isOn, setIsOn] = React.useState(false)
+
+  const onClick = () => {
+    setIsOn(!isOn)
+  }
+
+  const handleSwitchChange = on => {
+    console.log(`new switch "on" state: ${on}`)
+  }
+
+  return (
+    <>
+      <Box display="flex" maxWidth="300px">
+        <Box flexGrow={1} fontSize={2} fontWeight="bold" id="switchLabel">
+          Notifications
+        </Box>
+        <Switch onClick={onClick} onChange={handleSwitchChange} on={isOn} aria-labelledby="switchLabel" />
+      </Box>
+      <p>The switch is {isOn ? 'on' : 'off'}</p>
+    </>
+  )
+}
+
+render(Controlled)
+```
+
+### Small
+
+```jsx live
+<Box display="flex" maxWidth="300px">
+  <Box flexGrow={1} fontSize={1} fontWeight="bold" id="switchLabel">
+    Notifications
+  </Box>
+  <Switch aria-labelledby="switchLabel" size="small" />
+</Box>
+```
+
+### Delayed toggle with loading state
+
+```javascript noinline live
+const LoadingToggle = () => {
+  const [isLoading, setIsLoading] = React.useState(false)
+  const [isOn, setIsOn] = React.useState(false)
+
+  async function switchSlowly(currentOn) {
+    await new Promise(resolve => setTimeout(resolve, 1500))
+    return await !currentOn
+  }
+
+  async function onClick() {
+    setIsLoading(!isLoading)
+    const newSwitchState = await switchSlowly(isOn)
+    setIsOn(newSwitchState)
+  }
+
+  const handleSwitchChange = React.useCallback(
+    on => {
+      setIsLoading(false)
+    },
+    [setIsLoading]
+  )
+
+  return (
+    <>
+      <Box display="flex" maxWidth="300px">
+        <Box flexGrow={1} fontSize={2} fontWeight="bold" id="switchLabel">
+          Notifications
+        </Box>
+        <Switch
+          aria-labelledby="switchLabel"
+          isLoading={isLoading}
+          on={isOn}
+          onClick={onClick}
+          onChange={handleSwitchChange}
+        />
+      </Box>
+      <p>The switch is {isOn ? 'on' : 'off'}</p>
+    </>
+  )
+}
+
+render(LoadingToggle)
+```
+
+### Disabled
+
+```jsx live
+<Box display="flex" maxWidth="300px">
+  <Box flexGrow={1} fontSize={2} fontWeight="bold" id="switchLabel">
+    Notifications
+  </Box>
+  <Switch aria-labelledby="switchLabel" disabled />
+</Box>
+```
+
+### With associated caption text
+
+```jsx live
+<Box display="flex">
+  <Box flexGrow={1}>
+    <Text fontSize={2} fontWeight="bold" id="switchLabel" display="block">
+      Notifications
+    </Text>
+    <Text color="fg.subtle" fontSize={1} id="switchCaption" display="block">
+      Notifications will be delivered via email and the GitHub notification center
+    </Text>
+  </Box>
+  <Switch aria-labelledby="switchLabel" aria-describedby="switchCaption" />
+</Box>
+```
+
+### Left-aligned with label
+
+```jsx live
+<>
+  <Text fontSize={2} fontWeight="bold" id="switchLabel" display="block" mb={1}>
+    Notifications
+  </Text>
+  <Switch statusLabelPosition="end" aria-labelledby="switchLabel" />
+</>
+```
+
+## Props
+
+/\*\* Whether the "on" and "off" labels should appear before or after the switch.
+
+- **This should only be changed when the switch's alignment needs to be adjusted.** For example: It needs to be left-aligned because the label appears above it and the caption appears below it.
+  \*/
+  statusLabelPosition?: 'start' | 'end'
+
+<PropsTable>
+  <PropsTableRow name="aria-describedby" type="string" description="The id of the DOM node that describes the switch" />
+  <PropsTableRow
+    name="aria-labelledby"
+    type="string"
+    required
+    description="The id of the DOM node that labels the switch"
+  />
+  <PropsTableRow name="defaultOn" type="boolean" description="Uncontrolled - whether the switch is turned on" />
+  <PropsTableRow name="disabled" type="boolean" description="Whether the switch is ready for user input" />
+  <PropsTableRow name="isLoading" type="boolean" description="Whether the switch is ready for user input" />
+  <PropsTableRow name="on" type="boolean" description="Whether the switch is turned on" />
+  <PropsTableRow
+    name="onChange"
+    type="(on: boolean) => void"
+    description="The callback that is called when the switch is toggled on or off"
+  />
+  <PropsTableRow
+    name="onClick"
+    type="(e: MouseEvent) => void"
+    description="The callback that is called when the switch is clicked"
+  />
+  <PropsTableRow name="size" type="'small' | 'medium'" description="Size of the switch" />
+  <PropsTableRow
+    name="statusLabelPosition"
+    type="'start' | 'end'"
+    description={
+      <>
+        <div>Whether the "on" and "off" labels should appear before or after the switch.</div>
+        <div>
+          <Text fontWeight="bold">This should only be changed when the switch's alignment needs to be adjusted.</Text>{' '}
+          For example: It needs to be left-aligned because the label appears above it and the caption appears below it.
+        </div>
+      </>
+    }
+  />
+</PropsTable>
+
+## Status
+
+<ComponentChecklist
+  items={{
+    propsDocumented: true,
+    noUnnecessaryDeps: true,
+    adaptsToThemes: true,
+    adaptsToScreenSizes: true,
+    fullTestCoverage: true,
+    usedInProduction: false,
+    usageExamplesDocumented: true,
+    hasStorybookStories: true,
+    designReviewed: false,
+    a11yReviewed: false,
+    stableApi: false,
+    addressedApiFeedback: false,
+    hasDesignGuidelines: false,
+    hasFigmaComponent: false
+  }}
+/>

docs/src/@primer/gatsby-theme-doctocat/nav.yml

@@ -123,6 +123,8 @@
       url: /StyledOcticon
     - title: SubNav
       url: /SubNav
+    - title: Switch
+      url: /Switch
     - title: TabNav
       url: /TabNav
     - title: Textarea