Fix css-docs scripts

Created by: patrik-csak

• In css-compile-docs script, change docs.min.css to docs.css because it's not minified
• In css-prefix-docs script:
  • Point PostCSS at docs.css instead of docs.min.css
  • Exclude docs.min.css so it's consistent with the css-prefix script
• In css-minify-docs script, change clean-css input file from docs.min.css to docs.css
• Add docs.css and docs.css.map, which is consitent with the tracked built files in dist/css