Solution for gazillions of tabs

[Loirooriol]

The counter is already a bit too small for 4-digit numbers. If someone has more than 10^4 tabs, I guess it won't be readable in SVG, and I believe Webextension badges only display 4 characters.

I could try something like

	Int	Short	Long
1	1	1	1
12	12	12	12
123	123	123	123
1234	1k	1.2k	1234
12345	12k	12k	12.3k
123456	123k	123k	123k
1234567	1M	1.2M	1.23M
12345678	12M	12M	12.3M
123456789	123M	123M	123M

The "long" mode could use up to 5 characters but one being a narrow dot, so may be fine for SVG, but not for badges. The "short" mode never uses more than 4 characters, that's good. The "int" one is like "short" but without decimals; less information but maybe more clear.

I should investigate if they work well, and maybe add a pref to choose between them.