Add few instructions

[CarcajadaArtificial]

Hello! I'm a user of Deno Fresh, and most of my projects use a static CSS library developed by myself. Recently I've thought about purging the unused CSS of these projects and remembered about PurgeCSS. After stumbling upon this port for Deno, I was left wondering how to implement it for static CSS files on Fresh. I also found the PostCSS deno port, but I haven't found a way to make them interact or anything.
Any help is appreciated, thank you.