bug#49844: Highlight non-selected minibuffer prompt

[Juri Linkov]

>> here is the patch that implements this feature:
>
> I like it -- but does this need to be tied to
> minibuffer-depth-indicate-mode?  Indicating that the minibuffer isn't
> active in this way may be attractive even if you don't have that
> switched on?

Yeah, I don't like tying to minibuffer-depth-indicate-mode too.
But I have no idea where to put it otherwise.
Adding a new package for 25 lines makes no sense.