fix: tvOS compile error and appearance

[douglowder]

• Change to have tab bar correctly appear on first render (otherwise has the default gray color, and won't have correct appearance until tab selection changes)
• Fix compile error (UIFont.smallSystemFontSize unavailable on tvOS)

[okwasniewski]

Thanks for this! Looks like the issue with appearance is happening on iOS too, Im going to fix it in separate PR.

I will also rework the repo structure to be a monorepo so we can fit the Expo example and run tvOS/AndroidTV builds on CI to make sure it doesn't break all the time (sorry for that!)

[okwasniewski]

Thanks!