Migrate to MarkupContent and convert docstrings to Markdown

[krassowski]

Migrate from deprecated MarkedString to MarkupContent (fixes #21) and convert documentation strings to Markdown using docstring_to_markdown fixes #22, and supersedes #36.

Clients can now choose whether they prefer to receive plaintext or markdown markup by specifying:

• HoverClientCapabilities.contentFormat for hover,
• SignatureHelpClientCapabilities.documentationFormat for signature, or
• CompletionClientCapabilities.completionItem.documentationFormat for completions

and the client preference will be respected.

[krassowski]

I am also happy to transfer https://github.com/krassowski/docstring-to-markdown to python-lsp organization if you agree (I will obviously continue to maintain it and address any issues).

[ccordoba12]

I am also happy to transfer https://github.com/krassowski/docstring-to-markdown to python-lsp organization if you agree (I will obviously continue to maintain it and address any issues).

Sounds good to me.

[krassowski]

Done: https://github.com/python-lsp/docstring-to-markdown.

[cazador481]

It has been a while since this has been touched, is there any plans to release these changes?

[krassowski]

To celebrate one year anniversary of this pull request I resolved the merge conflicts 🎉. And all checks are still passing 💚.

[ccordoba12]

This looks pretty good to me, thanks @krassowski!

[ccordoba12]

@krassowski, last comments for you then this should be ready.

[ccordoba12]

Looks good to me now, thanks @krassowski!