Add more version upgrade tips

sr.ht/meta.sr.ht: add -billing subpackage

Update README.md with upgrade lessons

builds.sr.ht: bump pkgrel

dispatch.sr.ht: upgrade to 0.13.2

sr.ht/git-send-email.io: update to 0.1.9

paste.sr.ht: bump pkgrel

sr.ht/paste.sr.ht: upgrade to 0.9.0

sr.ht/builds.sr.ht: update to 0.52.4

sr.ht/py3-scmsrht: upgrade to 0.18.1

sr.ht/py3-srht: upgrade to 0.57.2

sr.ht/py3-pygithub: add setuptools to makedeps

sr.ht/py3-colour: add py3-wheel makedepend

sr.ht/py3-misaka: add missing dependency

sr.ht/py3-wheel: new aport

sr.ht/py3-cairosvg: re-introduce flake8/isort plugins

build.yml: use sr.ht 3.11 repository

sr.ht/py3-cairosvg: drop isort/flake8 plugins

build.yml: prefer abuild -r over abuild -R

sr.ht/py3-kombu: bump pkgrel