Redgifs media controls

Adds media controls for Redgifs

Press F to toggle fullscreen
Press Q to toggle quality
Press A to toggle all of the above
Press Space to toggle play/pause state
Press Right or Left arrows to seek +/- 5s
Press keys 0-9 to jump to specific point in time (0 = beginning, 9 = 90% of total duration)

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Known issues:
- Up / Down keys won't navigate between GIFs in fullscreen mode due to an issue with how Redgifs has implemented their UI. To mitigate this problem, exit fullscreen, scroll down to the GIF you want to view, and then go to fullscreen again