The behavior of the icon when enabling/disabling the extension has been fixed

This version adds back the behavior of switching to the next tab starting to play its video, though gated through an option which is disabled by default.

The extension now has a rich appearance. The behavior of cycling to first tab can now be controlled by a switch.

The tab activation mechanism has been greatly improved. First, it is run only if needed. Second it switches back to the current tab after activating the YouTube tab. This is done so fast that we don't see even a frame of the YouTube tab being activated, though I think it does trigger a pair of JS "visibilitychange" events on the window, but most pages do not listen to this event anyway.

I hope you like this new version. I'm open to ideas here on the firefox addon review section or on Github: https://github.com/mathieucaroff/youtube-tab-playlist/issues

Add an option to control whether to close the tab when the video finishes, and an option to disable the extension on the fly, all from the extension bar.
These features where mostly brought to you by an MR from **qsek**.

Youtube tab playlist v0.0.3

- fix the extension
- make it close the tab that finished playing
- except if it is the last youtube video tab open

Renamed from "Yt tab playlist" to "Youtube tab playlist"