rework compilation process

- minify (some) JS
- minify HTML output (markdown-it output, for example, isn't minified)
- switch stylus to SASS as stylus is not well maintained

Probably worth considering too:
- pre-gzip everything, reconfigure webserver to use that
- better parallelization

templates/layout.pug

@@ -12,7 +12,8 @@ html(lang="en")
             meta(name="description", content=description)
         link(rel="manifest", href="/assets/manifest.webmanifest")
         link(rel="shortcut icon", href="/assets/images/icon.png", type="image/png")
-        style= css
+        // this may be problematic but otherwise it overescapes stuff
+        style!= css
         if comments !== "off"
             script(src=`https://${domain}/isso/js/embed.min.js`, async=true, data-isso=`https://${domain}/isso/`)
     body