Code Actions on save

[hovsater]

Helix currently supports running Code Actions manually by pressing <space>+a. Some language servers also supports running specific code actions on save, e.g., typescript-language-server and gopls.

Preferably, we extend the language server configuration to allow for specifying code actions to run on save. The actions themselves would then run asynchronously, similar to what we already do for auto formatting.

[archseer]

I think this sounds reasonable, I'd add it as an array maybe? That's how the VSCode preference looks like if I remember correctly

[archseer]

Opened an issue from the discussion #1565