Add a toggle to the right hand upper corner of the screen to turn off the translation

The Chrome Extension once enabled right now cannot be turned off. This can become problematic for users if they hit a bug because of the extension or want to turn it off just for the sake of it.

They should see a toggle inside the popup which should turn off the changes caused by this app.
The toggle should be persisted in Chrome storage so that it does not disappear even if the user closes the app and opens it up later.

PS. You might need to add the storage context to the manifest file