Editor snapshots: added extra check for mac and ios for allowing screenshots

[srietkerk]

Fixes https://github.com/microsoft/pxt-minecraft/issues/2613

Just wanted to note that the disableFileAccessinMaciOs flag is something that gets set in the appTheme when the inGame=1 query variant exists. So there's a niceness because if the file access is disabled, we shouldn't allow for screenshots, but it also is a tell that we're in game for Minecraft.

Another point is that we are also setting disableFileAccessInAndroid to true with the inGame=1 query variant. I'm thinking about adding the check for that in the enableSnapshot function as well. However, I think leaving snapshots on for android is fine; at least testing in browser on my phone worked great. I would need to test on a Chromebook to see if it would work in game, though.

Upload target: https://minecraft.makecode.com/app/2255ed413beea760a738e01f155fc4d9e0fe2948-a1ffd9d0b1?inGame=1#editor
There should really only be a change with Mac/Ipad with this upload target, but, if you also want to check that nothing changes on windows/android, feel free to test!

[thsparks]

Per your description, I have a hunch that if disableFileAccessInAndroid exists, we should also respect that here. I agree it's worth testing, though if screenshots do work, I wonder if we should still check for it here but just not set the flag in the app theme.

Either way, this looks good to fix the bug!