Block Library documentation

Hi all,

Is there any documentation on Block Library?

wp-includes/css/dist/block-library/style.min.css

I mean, this is used by Gutenberg which aims to be used by everyone when the classic editor will be gone.

So I am surprised that I cannot find any documentation on which seems to be a custom CSS framework?

I really wish to use the block library style to avoid including other part of other CSS frameworks (Bulma, Bootstrap or whatever) for performance reasons.

Is there any documentation somewhere? Is it planned?

Thanks!