Merge branch 'main' of git.adrian.geek.nz:/srv/git/haskell-stylist into main

Tweak priority to be a list for the sake of cascadeLayers.

Remove Stylist-Traits APIs from Stylist Core, leaving backwards-compatible stubs.

Evaluate attribute namespace selectors.

Parse namespace selectors.

Improve documentation, release version 1.2

Rework psuedoelement infrastructure so they can be their own boxes.

Code cleanliness fixes.

Aid attribute sorting, fix install of internal modules.

Draft alternate API.