Hide video controls

[Arcus92]

The user might don't want to see the video controls all time. We should add an option to only show the controls if the mouse hovers over the bottom corner of the video element. The controls could move in and out with a little animation. There could be a very small, transparent indicator.

This should be toggled via a global settings menu. This could be show when clicking the extension icon in the browser toolbar. Currently the extension icon doesn't have any effect at all.