Inheritable modifiers

[kizu]

It would be a nice to have a more simple way of doing subj: for extend of styled-components we can't use nesting in CSS, so we'd need to have inheritable modfiiers, and in order to attach them more easily it would be nice to have some shortcut either on mod definition, or on call?

(also, I think, right now blockProps for mods on elems won't look at the default modifiers/props? its a really connected thing, so prob should be fixed in this scope)