Infra: Move numerical index to own page

[hugovk]

Fixes #2044.

Re: #2044 (comment)

The frontpage index (PEP 0) is very long, and starts the PEPs grouped by category, followed by a big table sorted by number.

This duplicates the PEP list (there's 655 right now), and can make searching in the page a bit confusing.

This PR creates a new numerical.html page with the numerical index.

I've kept the "Numerical Index" header on the frontpage and added a link to the new page. I moved the header up, before the remaining groups, but don't have a strong opinion on where this should be.

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📚 Documentation preview 📚: https://pep-previews--3992.org.readthedocs.build/numerical/

[willingc]

I love this @hugovk. Great usability improvement.

[AA-Turner]

Pushed one commit to remove the source link, GH review limitations etc etc.

A

[hugovk]

Thanks both for the reviews!

We now have an empty Contents sidebar:

We could remove the header, but some of the titles and author lists are pretty long, so shall we instead let this table be wider? Something like:

[AA-Turner]

so shall we instead let this table be wider

I'd perhaps left-align to where the sidebar is (was), but I would hesistate to make the table much wider than 60-64em (~900-950px), as it becomes difficult to read. For reference, GitHub's central area has a width of ~830px, and Wikipedia's new 'Standard' design has a width of ~950px.

A

[AA-Turner]

In local tests I used:

nav#pep-sidebar {
    display: none;
}
@media (min-width: 40em) {
    section#pep-page-section > article {
        width: 85%;
        float: unset;
    }
}
@media (min-width: 60em) {
    section#pep-page-section > article {
        max-width: 62em;
    }
}

[hugovk]

I had a go with that but the table of contents showed at the bottom of the page for PEP 0 and actual PEPs.

How does e439e06 look?