LSP integration

[filmil]

It might be interesting to turn private_comments into a LSP server. This would give you a worked-out UI and a ready-made integration for most modern editors. I couldn't figure out if the "write" sub-API would be supported by LSP, which leaves something to be desired, but I'm not giving up this avenue of thought just yet.

Granted, the LSP API is different from what private_comments uses today, but that seems fixable.

[filmil]

FWIW, I took a shot at https://github.com/filmil/private-code-comments.
This is a LSP server, and I wrote a rudimentary, and still rather buggy integration with Neovim.
It should be possible to integrate it with any LSP client.
The project shares no code base with private_comments, but is obviously inspired by it.