[Bugfix] Gracefully handle environments without window.matchMedia

[lsanwick]

I've been struggling with using Mantine within a test environment, and it seems like the dependency on window.matchMedia isn't really required in a test environment. This change simply guards against the case where window and window.matchMedia are not defined, and avoids trying to use it in that case.

I've looked at doing mocking based on the docs here, but this creates conflicts with other libraries, like framer-motion that assume if window.matchMedia exists, that they are not in a test environment.

[rtivital]

Thanks!