Add GMCP support?

[volundmush]

This isn't NECESSARY since you already have support for MDSP, but...

This is the ONLY THING your library is currently missing, as far as I can tell.

https://www.gammon.com.au/gmcp

So close to completionism! I might try to add this myself once I understand how this works better.

[KazDragon]

I would very much welcome the addition, and would be more than happy to work with you to add it, since I have no practical experience with GMCP myself and it would be an interesting project to take on.