Add support for `tmux` Control Mode

From discussion in #532, #1000:

If we're looking at tmux for things like splits, why not implement Tmux Control Mode like iTerm on MacOS. I switch back and forth between my Macs (with iTerm2) and my Surface Laptop with WSL but WSL2 combined with a really usable terminal (comparable to iTerm2) would really make me consider leaving the Apple camp.

In #532, from @zadjii-msft:

I did not know that Tmux Control Mode even existed. That sounds really awesome, I'm totally on board with trying to make that work somehow.

Was there any further thought put into this? I love tmux control mode - it's literally the only thing keeping me tethered to MacOS at work (since only iTerm supports it, and iTerm is mac-only). If it were implemented, I'd trash my Mac and request a Windows laptop immediately.

I'd love to see it listed as a post-1.0 milestone :)

We should do this.

Docs link: https://github.com/tmux/tmux/wiki/Control-Mode