Tactics in Scandinavian Def.

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* Redesigned app screens. You can set avatars now. Feel free to share your comments!
* Added new piece theme - "Kosal".
* Added colored King icon to indicate side to move in puzzles.
* Added popping up "Next" button after a puzzle.
* Improved lesson's exercises screen
* Improved tasks share option.
* Fixed dark screen in Practice on Android 11.
* Various fixes and improvements