Compress public/ in CI

.gitlab-ci.yml

@@ -5,6 +5,8 @@ pages:
   script:
     - npm install
     - npm run build
+    - apk add parallel brotli gzip
+    - parallel --will-cite "gzip -9 -k {} && brotli -k {}" ::: ./public/**
   artifacts:
     paths:
       - public