Slim down package

[joshuadavidthomas]

IMO, this package is a bit heavy for what it does -- provide an easy way to use Heroicons throughout your Wagtail admin. Odds are, someone doesn't need ALL the heroicons at their disposal, just a handful of either specific icons or just a specific style. Right now this package includes all of the heroicons for every style which adds roughly 2 MB to the package.

wagtail-heroicons/src/wagtail_heroicons on  main [$]  v3.12.1 (heroicons-3.12) 
➜ du -h
932K    ./templates/wagtail_heroicons/solid
932K    ./templates/wagtail_heroicons/outline
1.9M    ./templates/wagtail_heroicons
1.9M    ./templates
1.9M    .

This will be further exacerbated when we start using Heroicons v2 (#48) as it has not two, but four different styles of icons. So it could go to up as much as 4 or 5 MB just for the SVG templates alone.

We could either go the route described in #29 and have a different namespace package for each icon style and have them installable via extras -- python -m pip install wagtail-heroicons[solid] OR we could provide a way to opt in somehow to selecting individual icons. Perhaps a management command that allows someone to specifically select an icon to download and have it put in the templates directory of the user's project (or wherever they want it).

[joshuadavidthomas]

Alternatively, as also discussed in #29, we could write a template loader that can load templates from a zip file and use https://github.com/adamchainz/heroicons for the icons, since that's how that package provides the icons. Obviously this would be a bit more complex, and would require the user to add the template loader to their settings, but it's something to think about.

[joshuadavidthomas]

Though looking at django-template-partials source, it doesn't seem too difficult -- https://github.com/carltongibson/django-template-partials/blob/main/src/template_partials/loader.py