Add documentation for the debugger

[David-Else]

After a nightmare trying to get lldb-vscode installed (with terrible WIKI information), now I have all sorts of errors trying to debug Rust, but I don't know if I am doing things wrong or these are bugs in Helix.

Please can we have at least some basic documentation supplied. I am aware it is experimental, but if nobody knows how to try it there can be no feedback to take it to stable. Thanks!

EDIT: I have made a very limited start: https://github.com/helix-editor/helix/wiki/Debugger-Configurations#addendum-for-users-who-cant-make-any-of-the-above-work

[ondrej-ivanko]

Hi,

I agree with this proposition. I understand debugger is in experimental state, but it's already part of helix ecosystem and so should be documented at least in 'languages configuration section' of the documentation. There is no reference for languages.debugger keys. One can only experiment with values in default languages.toml file and hope for the best.

Btw. I never managed to make debugger for Rust to work and I tried pretty much everything. I'm using rust-gdb with dap-mode in Emacs.