Add lock-to-player button in miniworld

[dunity]

Add a button (& corresponding functionality) on the Miniworld workspace that locks the miniworld view to the player. The functionality should keep the player centered in the miniworld bounds (moving the Miniworld view accordingly in order to do so).

Consideration should be given later to allow for locking the view on the player at the bottom of the Miniworld bounds, or in the center. A button/toggle could offer such functionality.