Customization technique not requiring SASS

[longrunningprocess]

I'd like to see if @lucaslarroche would consider an additional customization option that would allow users to override pico defaults just using css vars? https://developer.mozilla.org/en-US/docs/Web/CSS/var

:root {
   ...
   var(--spacing, 1rem); /* provides the default fallback if the var isn't yet defined */
   ...
}

lots of customization questions that could be resolved this way (#135 , #219 , #366 , #390 , the new v2 https://v2.picocss.com/docs/css-variables#all-css-variables, #401)