Incorrect MIME type for *.js files

This commit closes #3

Caddy server relies on Alpine's file type MIME discovery,
which as of Alpine v3.20 is broken:

$ file --mime-type -b simple.js
> text/plain

Caddyfile

@@ -1,3 +1,4 @@
+# caddy reload --config /etc/caddy/Caddyfile
 {
 	order gitea before file_server
 }
@@ -7,3 +8,11 @@ gitea {
 	server {$GITEA_HOST} #   https://yourgitea.yourdomain.com
 	domain {$PAGES_DOMAIN} #             pages.yourdomain.com
 }
+
+@js {
+	path *.js
+}
+
+header @js {
+	Content-Type text/javascript # https://gitea.djmil.dev/djmil/gitea-pages/issues/3
+}