Integrate Marksman for Language Server Protocol

[kemelzaidan]

Describe your feature request

Language servers are a standard protocol for editors and IDE in order to provide advanced features for each language: https://langserver.org/

There is a nice LSP for markdown that would be a great addition to Marktext: https://github.com/artempyanykh/marksman

What problem does this feature solve? [optional]

The editor would gain advanced features like:

✅ Document symbols from headings.
✅ Workspace symbols from headings.
Query matching is subsequence-based, that is lsp will match both LSP and Low Seismic Profile.
✅ Completion for links (inline, reference, wiki).
✅ Hover preview for links.
✅ "Go to definition" for links.
✅ "Find references" for headings and links.
✅ Diagnostics for wiki-links.
✅ Support multi-folder workspaces.
✅ Custom parser for more fine-grained note structure.
✅ Rename refactor.