Makefile fixes and bug fixes relating to the major update

Pygments is stubbornly refusing to build for me. I'm dropping the
vendored package and it's vendored dependency (wcag_contrast_ratio).

Major updates

Updates to:
 + py3-srht
 + builds.sr.ht
 + git.sr.ht
 + lists.sr.ht
 + meta.sr.ht
 + todo.sr.ht
 + py3-asyncpg

Trying again with the updates to:
 + py3-ansi2html
 + py3-atpublic
 + py3-pygments

Re-releasing py3-pgpy.

Dropping py3-emailthreads.

Updating Alpine Linux to 3.17.

New build process

Packages can now be built with `make`. The targets are all based on the
files that are served in the official mirror.

Re-added two dependencies of todo.sr.ht that I has missed.