Responsive with container sizes

[sjstark]

Not really sure if it'd even be possible with current implementation, but it'd be pretty neat to get this so that responsive works with container queries as well as css layout media queries.

[weotch]

Yeah, I think it would be totally possible and probably a pretty small change. Like

• Add a use-container-queries boolean prop
• Add a container-name prop
• Update the media queries that are generated in src/concerns/responsive.coffee (maybe there is just one?) to conditionally write container queries instead, based on that prop