Add PostCSS to build process

[d13]

Adds extra control how styes are rendered. We can take advantage of browserlist settings to optimize for web and desktop build targets without changing our source styles.

• [ ] Look at postcss-preset-env (https://github.com/csstools/postcss-plugins/tree/main/plugin-packs/postcss-preset-env#plugins-list)
  • Options: https://github.com/csstools/postcss-plugins/tree/main/plugin-packs/postcss-preset-env#browsers
• [ ] Add autoprefixer (https://github.com/csstools/postcss-plugins/tree/main/plugin-packs/postcss-preset-env#autoprefixer)
  • Options: https://github.com/postcss/autoprefixer#options
• [ ] Add postcss-short plugin (https://github.com/csstools/postcss-short)
• [ ] CSSNano (https://cssnano.co/)