refactor: move extension APIs to session.extensions (#45597)

refactor: move extensions to session.extensions

docs/api/extensions-api.md

@@ -0,0 +1,124 @@
+## Class: Extensions
+
+> Load and interact with extensions.
+
+Process: [Main](../glossary.md#main-process)<br />
+_This class is not exported from the `'electron'` module. It is only available as a return value of other methods in the Electron API._
+
+Instances of the `Extensions` class are accessed by using `extensions` property of
+a `Session`.
+
+### Instance Events
+
+The following events are available on instances of `Extensions`:
+
+#### Event: 'extension-loaded'
+
+Returns:
+
+* `event` Event
+* `extension` [Extension](structures/extension.md)
+
+Emitted after an extension is loaded. This occurs whenever an extension is
+added to the "enabled" set of extensions. This includes:
+
+* Extensions being loaded from `Extensions.loadExtension`.
+* Extensions being reloaded:
+  * from a crash.
+  * if the extension requested it ([`chrome.runtime.reload()`](https://developer.chrome.com/extensions/runtime#method-reload)).
+
+#### Event: 'extension-unloaded'
+
+Returns:
+
+* `event` Event
+* `extension` [Extension](structures/extension.md)
+
+Emitted after an extension is unloaded. This occurs when
+`Session.removeExtension` is called.
+
+#### Event: 'extension-ready'
+
+Returns:
+
+* `event` Event
+* `extension` [Extension](structures/extension.md)
+
+Emitted after an extension is loaded and all necessary browser state is
+initialized to support the start of the extension's background page.
+
+### Instance Methods
+
+The following methods are available on instances of `Extensions`:
+
+#### `extensions.loadExtension(path[, options])`
+
+* `path` string - Path to a directory containing an unpacked Chrome extension
+* `options` Object (optional)
+  * `allowFileAccess` boolean - Whether to allow the extension to read local files over `file://`
+    protocol and inject content scripts into `file://` pages. This is required e.g. for loading
+    devtools extensions on `file://` URLs. Defaults to false.
+
+Returns `Promise<Extension>` - resolves when the extension is loaded.
+
+This method will raise an exception if the extension could not be loaded. If
+there are warnings when installing the extension (e.g. if the extension
+requests an API that Electron does not support) then they will be logged to the
+console.
+
+Note that Electron does not support the full range of Chrome extensions APIs.
+See [Supported Extensions APIs](extensions.md#supported-extensions-apis) for
+more details on what is supported.
+
+Note that in previous versions of Electron, extensions that were loaded would
+be remembered for future runs of the application. This is no longer the case:
+`loadExtension` must be called on every boot of your app if you want the
+extension to be loaded.
+
+```js
+const { app, session } = require('electron')
+const path = require('node:path')
+
+app.whenReady().then(async () => {
+  await session.defaultSession.extensions.loadExtension(
+    path.join(__dirname, 'react-devtools'),
+    // allowFileAccess is required to load the devtools extension on file:// URLs.
+    { allowFileAccess: true }
+  )
+  // Note that in order to use the React DevTools extension, you'll need to
+  // download and unzip a copy of the extension.
+})
+```
+
+This API does not support loading packed (.crx) extensions.
+
+**Note:** This API cannot be called before the `ready` event of the `app` module
+is emitted.
+
+**Note:** Loading extensions into in-memory (non-persistent) sessions is not
+supported and will throw an error.
+
+#### `extensions.removeExtension(extensionId)`
+
+* `extensionId` string - ID of extension to remove
+
+Unloads an extension.
+
+**Note:** This API cannot be called before the `ready` event of the `app` module
+is emitted.
+
+#### `extensions.getExtension(extensionId)`
+
+* `extensionId` string - ID of extension to query
+
+Returns `Extension | null` - The loaded extension with the given ID.
+
+**Note:** This API cannot be called before the `ready` event of the `app` module
+is emitted.
+
+#### `extensions.getAllExtensions()`
+
+Returns `Extension[]` - A list of all loaded extensions.
+
+**Note:** This API cannot be called before the `ready` event of the `app` module
+is emitted.