Make Commet buildable and Runnable in macOS and iOS

[polemarkh]

This makes it possible to create commet desktop and iOS apps, and the iOS app is confirmed to pass App Store beta review.

[Airyzz]

Thanks, this is quite exciting!

Would you be able to setup actions to build for macos, as at this point I can't really test that this actually works, so that would be super helpful!

[polemarkh]

I think that's added an action that should (hopefully) build for Mac. I want to make sure that it works before I add one that builds for iOS.

[polemarkh]

My base status here is that the macOS build is failing, but it's failing because the base64 decode of the certificate (that I have as a secret) is failing, and I'm having trouble figuring out why it's failing. There may well be other bugs as well, but until this part is figured out, there's no good way to check that, because the runner never actually gets to the point where it's trying to build the macOS binary.