Allow title and fragments in PEP and RFC references

[AA-Turner]

This patches Docutils in pep2html to allow the syntax of :pep:`title <3000#section>`. Users of Sphinx will be familiar with this, and e.g. in #2248 there is no clean way to express the author's intent without this.

Passing test run at https://github.com/AA-Turner/peps/runs/4872058326 -- from this commit AA-Turner@5449914

cc @JelleZijlstra (you've merged a few of my recent ones so sorry for taking advantage of your good nature!)

A

[JelleZijlstra]

Would it be feasible to start writing unit tests for this script?

[Rosuav]

Ooh that looks useful. I like it.

[AA-Turner]

Would it be feasible to start writing unit tests for this script?

For pep2html? I wonder if it would be worth the time investment given PEP 676? (Of course, 676 could be rejected!)

The inspiration for the code here was taken from Sphinx, although I used a function based method -- as Sphinx does a lot more they implement a few base classes etc.

I want to upstream this logic into Docutils, but that project doesn't move amazingly quickly.

A

[JelleZijlstra]

Ah, I didn't realize PEP 676 would replace this. Let's just merge as is then.