Support visionOS

[frlefebvre]

My current app currently does not compile because of the Mixpanel library. As far as I can tell, all it needs is a few #if os(visionOS) statements to be added so the right libraries get imported.

Keep up the good work!

[jaredmixpanel]

@frlefebvre Please feel free to submit a PR and we'll take a look.

[frlefebvre]

@jaredmixpanel I'm going on holiday for a couple weeks but I'll take a look when I'm back.