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

Dockerfile

@@ -92,10 +92,6 @@ COPY . .
 # fmt-check` is the markdown-check stage above.
 RUN if [ -n "$(gofmt -s -l .)" ]; then echo "gofmt needed on:"; gofmt -s -l .; exit 1; fi
 
-# static/static.go embeds the Alpine.js file this extracts from 3p/; without
-# it the static package does not compile and cannot be linted.
-RUN script/assets
-
 # The golangci-lint steps run with --network=none. `golangci-lint config
 # verify` is documented as fetching its JSON schema over HTTPS; this pinned
 # image resolves the schema without any network, and --network=none enforces
@@ -130,9 +126,6 @@ RUN go mod download
 
 COPY . .
 
-# static/static.go embeds the Alpine.js file this extracts from 3p/.
-RUN script/assets
-
 # -timeout applies to each package on its own, so 90s has only to clear the
 # slowest one. -p 4 -parallel 8 keep the run under 2 GB of memory: at most
 # four test binaries build or run at once, each with at most eight parallel
@@ -211,10 +204,8 @@ RUN version="$(make version VERSION="$VERSION")"; \
         esac; \
     fi
 
-# Builds through the Makefile's build target, which runs script/assets
-# (Alpine.js, extracted from its tarball in 3p/) first. The target builds
-# with cgo off, so the binary is statically linked and runs on the Alpine
-# runtime image below as it is.
+# The Makefile's build target builds with cgo off, so the binary is
+# statically linked and runs on the Alpine runtime image below.
 RUN make build VERSION="$VERSION"
 
 # Runtime stage