Create a CSS Library|Framework from SASS in Block Library for theme developers

[overclokk]

I know that with Global Styles we will change all block styles, but I think something like a CSS library/framework (named as you like) could be very usefull for theme developer that uses Bootstrap or Tailwind or other thing.

If we had such a library we could have an easy way to generate the remaining CSS that we need for ours themes, the one not generated by the global style.

With that library I could use npm to import it in my theme and then develope what I need for all block I use in the site instead of loadiing this https://github.com/WordPress/gutenberg/tree/trunk/packages/block-library/src

This was something I had in mind from some months, you can read more here https://wordpress.slack.com/archives/C02RP4Y3K/p1614796355237500

[overclokk]

Let's start with some basic idea, styling buttons, for now I add 2 issue to follow here: #34196 and #34198