Offer to install codechat server if it is missing

[oscarlevin]

Specifically for the VS Code extension, it would be helpful if upon discovering that codechat_server is not installed, the extension offered to run pip install codechat_server. This is what I do for pretext-tools and pretext. I could implement the step there, but it might be of wider interest.

If you agree this is a desired feature, I could contribute it here.

[bjones1]

That makes a lot of sense, with a few caveats: outside of Codespaces, I prefer to install the server in a Python virtual environment. I'd definitely welcome your contribution with this -- I would think you'd want to add code starting here.