Add a `colorize_tab` input binding

[mitchellh]

From #11082

Add a new input binding colorize_tab:<color> that can be used to set the tab color. This will only work on macOS since only macOS supports tab coloring.

[gurgeous]

while you are in there, let me make the circle a lot bigger :)

[00-kat]

That sounds completely unrelated to this. Open a new discussion (if one doesn't exist already).