Links outside Lichess should not be opened in-app

[forgottosave]

Description

As this app is basically a chopped down browser, opening links not related to Lichess is still possible. While this doesn't sound so bad, it actually breaks the functionality, as all browser navigation possibilities are not present.

Solution: The app should redirect any outside links to another browser or app on the phone

To Reproduce

1. go on the Lichess start page
2. click on any outside link ("swag store", twitch,...)