Add TerminalMode hl group (or update readme/docs?)

[Darren Brierton]

I see that in #11 you did something to add terminal mode support. But the readme and docs don’t mention anything about that, should there be a new hl group TerminalMode?

Modicator.mov

[Melker Ulander]

Yes there's a TerminalMode and TerminalNormalMode highlight. Thanks for reminding me to add them to the docs! 🙂