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

README.md

@@ -1,6 +1,6 @@
 <h1>
     <div align="center">
-        <img alt="ReplayWebpage" src="assets/replaywebpage-lockup-color-dynamic.svg" width="90%">
+        <img alt="ReplayWebpage" src="src/assets/brand/replaywebpage-lockup-color-dynamic.svg" width="90%">
     </div>
 </h1>