refactor: migrate app to Alpine.js

vendor/README.md

@@ -8,3 +8,8 @@ retain their embedded authorship and license notices unchanged.
 
 No CDN or npm installation is needed at runtime. Font data is loaded locally
 when selected and saved in a separate browser cache for later offline use.
+
+`alpine.js` is the unmodified ES module build of
+[`Alpine.js 3.14.9`](https://github.com/alpinejs/alpine/tree/v3.14.9).
+Its MIT license is retained as `alpine.LICENSE`. The bundled Vue reactivity
+code's MIT license is retained as `vue.LICENSE`.