docs: add Document and Workspace symbol example server

[alcarney]

Description (e.g. "Related to ...", etc.)

Another example server, this time implementing the textDocument/documentSymbol and workspace/symbol requests

Code review checklist (for code reviewer to complete)

• [ ] Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• [ ] Title summarizes what is changing
• [ ] Commit messages are meaningful (see this for details)
• [ ] Tests have been included and/or updated, as appropriate
• [ ] Docstrings have been included and/or updated, as appropriate
• [ ] Standalone docs have been updated accordingly

Automated linters

You can run the lints that are run on CI locally with:

poetry install --all-extras --with dev
poetry run poe lint

[alcarney]

even writing your own programming languages now

Mainly to try and make the language "parsing" code as simple as possible so we can focus on the LSP stuff :)

Could you approve it again? You were a bit quick on the draw I'm afraid :sweat_smile:

[alcarney]

Thanks!