Add possibility to hide rating

[poettler-ric]

New players (like me) often get anxious about their rating and are to hesitant to play. The lichess web page added the possibility to hide player ratings. Something similar on the mobile client would be amazing. This feature could also be extended to puzzles.

[surfstian]

Use zen mode in settings.

[teake]

Use zen mode in settings.

Not quite the same. On web, setting Show player ratings to No will remove all mentions of ratings everywhere: not only while playing, but also on e.g. the profile pages and the games history. If you don't want to know your (or your opponent's) rating, you'd have to steer clear of those sections of the app on mobile.

Also, zen mode remove some UI elements I find useful -- I just want to hide the ratings, nothing else.