Infrastructure: netlify

• Documentation previews for PRs and releases are deployed (https://github.com/sagemath/sage/blob/develop/.github/workflows/doc-publish.yml) to netlify by the github workflow [doc-publish.yml].

  Example sites: https://doc-release--sagemath.netlify.app/html/en/reference/index.html

• Documentations for old Sage versions are maintained in netlify, and accessible by "old versions" link in any Sage documentation page.

• Secrets NETLIFY_AUTH_TOKEN, NETLIFY_SITE_ID are stored in sagemath/sage/Settings/Security/Repository secrets.

• admin as of 2024-06: @kwankyu (see #34874)