YouTube Rewind & Fast Forward Buttons

Add Rewind & Fast Forward buttons to videos player in a YouTube site/r/nAs a default, they are the same as the Left / Right arrow keys. 5 seconds each.

On the options page you can: 

1. Change the seconds for each button individually. 
2. Set to override the arrow keys to update the video time with the same seconds as in the Rewind &  Fast Forward buttons seconds. (default is not to override)