document commands

[trinity-1686a]

commands don't appear to be well documented. I've searched in the repository and on the web, and the only thing I found is README.txt on some branches, however it's probably not up to date as those branches haven't been touched in months

[leumasme]

Would suggest creating docs on the github Wiki page, which is already activated for this repo, but unused.
For now, you can check /chelp, the ingame command autocompletion or join the discord for help.

[Earthcomputer]

I probably won't get round to command documentation until I one day feel like it, feel free to edit the wiki yourself with some documentation, that would be awesome.

[ImUrX]

tag this with need help, would be nice to have it like that