Implement IndexNow in RTD for SEO

[MicahGale]

Bing (and most search engines) now support IndexNow. Here's a blog on it: https://lazarinastoy.com/the-ultimate-guide-to-microsoft-indexnow-api-indexation-protocol-for-search-engines-with-python-code-examples/

Tl;dr: you can now tell a search engine a new page exists rather than waiting for their webcrawlers.

I'm thinking every version release (and maybe stable/latest) RTD then tells IndexNow about the news pages with this PyPI package: https://pypi.org/project/indexnow/.

Alternative: we make a sphinx plugin so you can run: make indexnow or something like that.