docs: mark contextBridge as experimental (#20638)

* docs: mark contextBridge as experimental

This commit didn't make it to the original PR, quick addition here

* Update context-bridge.md

docs/api/context-bridge.md

@@ -40,7 +40,7 @@ context isolation and what it affects in the [BrowserWindow](browser-window.md)
 
 The `contextBridge` module has the following methods:
 
-### `contextBridge.exposeInMainWorld(apiKey, api)`
+### `contextBridge.exposeInMainWorld(apiKey, api)` _Experimental_
 
 * `apiKey` String - The key to inject the API onto `window` with.  The API will be accessible on `window[apiKey]`.
 * `api` Record<String, any> - Your API object, more information on what this API can be and how it works is available below.
@@ -49,7 +49,7 @@ The `contextBridge` module has the following methods:
 
 ### API Objects
 
-The `api` object provided to [`exposeInMainWorld`](#contextbridgeexposeinmainworldapikey-api) must be an object
+The `api` object provided to [`exposeInMainWorld`](#contextbridgeexposeinmainworldapikey-api-experimental) must be an object
 whose keys are strings and values are a `Function`, `String`, `Number`, `Array`, `Boolean` or another nested object that meets the same conditions.
 
 `Function` values are proxied to the other context and all other values are **copied** and **frozen**.  I.e. Any data / primitives sent in