Add .rst to mimetypes

[tucked]

>>> import mimetypes
>>> mimetypes.guess_type("README.rst", strict=False)
(None, None)

In the python:3.11 Docker image, we get a vanity type:

>>> mimetypes.guess_type("README.rst", strict=False)
('text/prs.fallenstein.rst', None)

I think most people would expect text/x-rst. Even better would be to get it registered!

Linked PRs

• gh-101137: Add text/x-rst to mimetypes #118593
• [3.12] gh-101137: Add text/x-rst to mimetypes (GH-118593) #118599

[sobolevn]

Related: #17995

[jaraco]

Given that this type is explicit in packaging specifications, it would be valuable for Python to support inferring it from an extension and avoid hacks like these.

[sobolevn]

I am on it :)