ci(*): automate docs publishing

[vdice]

• Adds a docs.yml workflow to publish (re-)generated docs to a gh-pages branch: 1170372
• Updates the generate_docs.py script to take in a versioned folder arg (eg v4 or the canary default): e9ec38f
• Updates the script to (re-)write an index.html file at root to redirect to the most recent major version (using the same arg as above, when in v* form): 8048880
• Removes docs/ and adds this folder to .gitignore: 1730e61

TODO:

• actually create the gh-pages branch seeded with docs/{v1-v4} folders
  • Note: currently not planning to bring over html files outside of a versioned subfolder (today they appear to represent v2 docs); with the intention that the only such file will be the redirect root index.html

Tested on my fork:

• branch: https://github.com/vdice/spin-python-sdk/commits/gh-pages
• latest/working workflow run: https://github.com/vdice/spin-python-sdk/actions/runs/24426152550
• docs site: https://vdice.github.io/spin-python-sdk/

Closes #141

[dicej]

Thanks!

Would you mind removing the docs/** linguist-generated=true line from .gitattributes, also, since it's no longer needed?