Consider adding support for CSS breakpoing / media queries in ThemeBuilder.

https://developer.mozilla.org/en-US/docs/Web/CSS/CSS_media_queries/Using_media_queries 

https://www.w3schools.com/howto/howto_css_media_query_breakpoints.asp 

This will enable users to create response design directly within the ThemeBuilder application.

Requested through t.1682156