add diagnostics signs.

[prabirshrestha]

Although vim-lsp already supports :LspDiagnostics it would be good to have diagnostics signs working.

Seems like @tsufeki already got it running. https://github.com/tsufeki/vim-lsp/tree/diagnostic-signs. Any plans to send PR soon for this?

Ideally I would like to have another vim plugin that manages these signs and vim-lsp uses it. This ways other plugins besides vim-lsp can also work on it. Had posted my initial thoughts to ale but got rejected. dense-analysis/ale#517 (comment)

Would love to have the api look somewhat like VsCodes' DiagnosticsCollection simple and clear. https://code.visualstudio.com/docs/extensionAPI/vscode-api#DiagnosticCollection

[prabirshrestha]

This is now supported by #89 and #90.

[nickspoons]

@prabirshrestha I realise this is already implemented but have you seen that ALE now does, in fact, support allowing external plugins to send diagnostics? ALE provides an ALEWantResults User autocmd, see dense-analysis/ale/issues/2017.

This is now being used in OmniSharp-vim, see here and here

It could be worth providing an option to use ALE signs rather than vim-lsp signs. This would allow users who already use ALE for other things to use their same ALE sign configuration for LSP diagnostics, and also use their same mappings for navigating between diagnostic results.

Would you be interested in this, if I put together a PR?