v0.14 - Wagtail 5.0, iconified

This release:

• 🚀 switches to using ruff instead of isort/flake8
• 📦 switches to flit for packaging
• 🛠️ adds support for for Wagtail 5.0 (chiefly by switching to using BaseChoose instead of the now removed AdminChooser)
  • also tests against Python 3.11, and Django 4.2 with Wagtail 5.0
• 🎨 adds audio/video icons (usable via their ids: wagtailmedia-audio, wagtailmedia-video)

Relevant PRs: #199 and #201

Full Changelog: v0.13.0...v0.14.0