We should have a page similar to the LBS extension's 'action.html' page [1].

Before invoking the alternative browser, BrowserSwitcher opens the chrome://browserswitch page, with a message telling the user what is going on.

If launching the alternative browser fails for whatever reason, we can also use this space to show an error message.

We should also let admins configure a delay before the alternative browser is launched.

[1] https://github.com/LegacyBrowserSupport/legacy-browser-support/blob/master/chrome_extension/action.html