Update YouTubeEmbeddedPlayerScrubber.js

[georgedorn]

Thanks for creating this. I was annoyed, but not quite annoyed enough to start a greasemonkey script myself.

But now that it exists, I made a few changes for my own. Feel free to steal, ignore, modify, tweak, anything about this that you want.

• Show the playback speed as an icon next to the others in the lower left
• Hide/show the UI in a similar way to the player's own UI. There might be a more graceful way to hook into the player's events or set the timings to match, but this works good enough for me.