Created by: andresgalante
This PR fixes #23915 (closed) and it looks like this:
Notice that I had to reverse the order of the declarations on the _navbar.scss putting first themes and then breakpoints to avoid increasing specificity on themes.
also, I've created variables for dropmenu styles on navbar so users have full control of them.
@mdo @XhmikosR @Johann-S Since this is not a tiny change I did as much test I could and I think it's solid, but a fresh pair of eyes is really welcome