Add YouCompleteMe as a LSP option for vim/neovim

[weihanglo]

As YouCompleteMe supports arbitrary LSP implementation, it could be added to the list of vim LSP implementation. It works like a charm.

[matklad]

bors r+

Thanks!

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript

[flodiebold]

Isn't YCM the one that doesn't support snippet completions? 😬

[matklad]

It is one, but it probably supports other features (like goto def), and having it in the manual makes fixing the underlying issue on our side more likely :)

[bstaletic]

Isn't YCM the one that doesn't support snippet completions?

Yes, but since #4117, this isn't a showstopper (thanks to @matklad). Everything that I bothered to test worked as intended.

However, the link in this PR is bad, as it explains how to set RLS up. The rust-analyzer guide is here.

@matklad Do you want me to submit another PR to fix this?

[matklad]

@matklad Do you want me to submit another PR to fix this?

Yup, that would be helpful! To be fair, I just blindly merge all PRs regarding vim installation instructions without deep inspection, as I don't know a lot about them, and there are many options for vim.

[weihanglo]

Sorry for the bad link. @bstaletic is right. We do not need --rust-completer flag for YCM setup because it would trigger the installation of rls.