Add ConEmu-specific escape codes

[DRSDavidSoft]

ConEmu

I'd like to add some of the ConEmu-specific escape codes via a PR if it's okay with you.

documentation:
https://conemu.github.io/en/AnsiEscapeCodes.html#ConEmu_specific_OSC

For example, the equivalent to this iTerm 2 sequence:

ansi-escapes/index.js

Line 129 in 5f93eca

x.iTerm.setCwd = (cwd = process.cwd()) => `${OSC}50;CurrentDir=${cwd}${BEL}`;

Would be this for ConEmu:

x.ConEmu.setCwd = (cwd = process.cwd()) => `${OSC}9;9;${cwd}${BEL}`; 

per the documentation:

Sequence	Description
ESC ] 9 ; 9 ; “cwd” ST	Inform ConEmu about shell current working directory.

[sindresorhus]

Sure, PR welcome :)

[sindresorhus]

We could then also add a general setCwd method which uses iTerm.setCwd on iTerm and ConEmu.setCwd on ConEmu.