Site reorg: Remove site/ subpath (#306)

Unfortunately, for proper package pathing, need to remove the `site/`
subpath. This includes:
- Moving everything back into root
- Adding a `copy-site.sh` script to copy resources into `mkdocs/site/`
before building the site with mkdocs.
- Also update examples to ensure all are loading the local sw.js / ui.js
- Consolidate examples in `docs/examples`
- Consolidate assets under src/assets/
- Move `favicons` to root
- Reformat and relint
- Tests: update playwright tests to use mkdocs output, add test for
embed in docs
- bump to 2.0.0-beta.2

mkdocs/site/docs/overrides/main.html

@@ -0,0 +1,6 @@
+{% extends "base.html" %}
+
+{% block icons %}
+  {% set icon_path = "overrides/.icons/bootstrap/" %}
+  {{ super() }}
+{% endblock %}