Enable Brotli compression

- Compress file AOD.
- Let the server only use static files. 
- Don't add github-pages to jekyll-plugins group, due to the fact github-pages will behave differently when enabling production ENV.
- Adds an extra 10s for the `host` to use `./buid.sh` due to compressing all files.
- Resolves #2186

build.sh

@@ -1,4 +1,4 @@
 #!/usr/bin/env sh
 set -e # halt script on error
 
-bundle exec jekyll build
+JEKYLL_ENV=production bundle exec jekyll build