Commit Alpine.js to the repo instead of unpacking it at build time (closes #163)

static/js/alpine.min.js is now committed: package/dist/cdn.min.js from
the @alpinejs/csp 3.14.9 npm package, byte for byte, taken once from the
package file that was in 3p/. The build no longer unpacks it, so
script/assets, the assets make target, its Dockerfile steps and the
ignore entries for the file are gone, and so is the package file.
Prettier and ESLint both ignore the file, so it stays as published.
Comments and the README now describe the committed file.

Model: opus-5-5

.dockerignore

@@ -72,10 +72,8 @@
 **/*.sublime-*
 
 # This repository's own host-built artifacts: the binary `make build`
-# writes, and the Alpine.js file `make assets` extracts from 3p/ (the
-# build extracts its own).
+# writes.
 /bin
-/static/js/alpine.min.js
 
 # SQLite databases, which hold the session key and webhook payloads, at
 # any depth.