feat(lsp): support ddc_source_lsp server capabilities

[psuong]

• Adds support for ddc_source_lsp capabilities

  • Creates an array of tuples ( mod_name, server_capability_callback) and picks the first supported capability available for autocompletion plugin with nvim-lsp

  Testing Reqs

• Ran luarocks test with 8 successes (no new tests added)

[github-actions]

Review Checklist

Does this PR follow the Contribution Guidelines? Following is a partial checklist:

Proper conventional commit scoping:

• For example, fix(lsp): some lsp-related bugfix

• Pull request title has the appropriate conventional commit prefix.

If applicable:

• Tested
  • Tests have been added.
  • Tested manually (Steps to reproduce in PR description).
• Updated documentation.
• Updated CHANGELOG.md

[mrcjkb]

Hey 👋

thanks for the PR 🙏
I don't want to add too many plugins' client capabilities automatically, because that decreases stability (especially when it's a plugin that doesn't have SemVer releases, or one that I can't dog feed myself).

I'm actually thinking of removing the existing code that automatically adds other plugins' client capabilities and perhaps suggesting to upstream an API for registering capabilities with Neovim core, so that plugins can register themselves.

[psuong]

Alright, that makes sense, I'll keep a look out for that api in the future