use browser extension api for tab group management

[Gotos]

This should fix #1480 and also make the need for a chrome extension for tab groups obsolete.

I wasn't sure how to handle the locales, so most languages will probably still claim you need that separate chrome extension for tab groups; I only fixed the text for languages I know decently well.

[mohamad-supangat]

hai @Gotos can you help me to using your pull request ?

[agm-eratosth]

@sienori Can we get this pull request reviewed and approved somehow? Tab groups in firefox is a very frequent request within the issues of this extension.

If you don't have time I wouldn't mind reviewing and filling in approving this pull request, although it would require some learning on my part.

[mikelei8291]

For the locales you probably only need to update the English version. All the other languages are translated on Crowdin and synced back to GitHub regularly. Updating the strings directly on GitHub will likely get them overridden in the next sync from Crowdin.

[SALYAVIA]

Please explain how to install this code. Install using developer mode?

[sciafri]

Hi - so I just tested this. It seems to work well, however the name of the tab group isn't restored.