Document the python/proofreaders team

[hugovk]

Fixes #886.

Add the last paragraph here:

---

📚 Documentation preview 📚: https://cpython-devguide--1229.org.readthedocs.build/documentation/help-documenting/#proofreading

[ezio-melotti]

Suggested change

	For help with the finer points of English technical writing, mention the
	`@python/proofreaders <https://github.com/orgs/python/teams/proofreaders>`__
	team in your issue or pull request in any `@python <https://github.com/python/>`__
	repo. If you'd like to join the team,
	`open a core-workflow issue <https://github.com/python/core-workflow/issues/new/choose>`__
	similar to
	`python/core-workflow#461 <https://github.com/python/core-workflow/issues/461>`__.
	.. _issue tracker: https://github.com/python/cpython/issues
	For help with the finer points of English technical writing, mention the
	`@python/proofreaders`_ team in your issue or pull request in any `@python`_ repo.
	If you'd like to join the team, `open a core-workflow issue <proofreaders-issue>`_.
	.. _issue tracker: https://github.com/python/cpython/issues
	.. _@python/proofreaders: https://github.com/orgs/python/teams/proofreaders
	.. _@python: https://github.com/python/
	.. _proofreaders-issue: https://github.com/python/core-workflow/issues/new?assignees=&labels=&projects=&template=proofreader_membership.md&title=Request+for+Python+Proofreaders+team+membership%3A+name

I updated the link to the new template and moved it at the end together with the others. I hope I got the syntax right 🙃

I was also wondering if there are any restrictions for joining the group -- do people that send requests need to be already part of the python org (e.g. as triagers)? If so, we should mention that too.

[hugovk]

Good question, asked at #886 (comment)

[hugovk]

Answer:

At the moment, there aren't any restrictions. (Of course, that might change if people start abusing this somehow.)

#886 (comment)

So nothing to mention right now.