Added media selectors to exclude menu hacks from macos clients

[philberthfz]

Adds media selectors on the import statement and to the hacks overrides which directly deal with the menu-bar padding to prevent these from being loaded on Macintosh clients. This removes the empty gap at the top of the window where the menu bar ought to go.

This fixes #43 , at least insofar as hiding a problem fixes it. Obviously, limitations of Firefox on mac mean we can't have the menu bar properly inside the application, but considering that's the way MacOS has always worked, I'm satisfied with the outcome.

In my admittedly limited testing it doesn't appear to break anything on Linux, at least on my machine. Tested on the latest Firefox (144.0.2) as well as the ESR release (140.4.0esr) both on XFCE and it appears to work as I'd expect on those platforms - menu bar shows up as expected and with the appropriate padding.

And obviously I tested it on MacOS, where it did what I wanted it to: not show the empty space where the menu bar was supposed to go.

[soup-bowl]

This actually highlights an interesting bug when used on Linux (perhaps Windows too), that if you didn't go in an enable the menu bar before enabling the theme, it will now show a blank space instead.

From the codespace that runs a fresh install:

I might do some digging into this however, as this may open up the possibility to do some conditional spacing so that the menubar can be option on Linux too. I've just been waiting for some time to free up so I could do some theme refactoring.