feat(iOS): add an option to prevent dismissal of external modals

[Ubax]

Description

In some cases, dismissing a modal not owned by RNScreens may not be the expected behavior.

Changes

Added a new protocol, RNSDismissibleModalProtocol, which can be used by external libraries to control whether their modal should be dismissed when pushing a screen’s modal on top.

When dismissing the top modal, the code now checks for conformance to this protocol. If the modal implements the protocol and isDismissible is true, the dismiss will not happen.

In all other cases, the behavior of setModalViewControllers remains the same as before this change.

Test code and steps to reproduce

Checklist

• Included code example that can be used to test this change
• Updated TS types
• Updated documentation:
  • https://github.com/software-mansion/react-native-screens/blob/main/guides/GUIDE_FOR_LIBRARY_AUTHORS.md
  • https://github.com/software-mansion/react-native-screens/blob/main/native-stack/README.md
  • https://github.com/software-mansion/react-native-screens/blob/main/src/types.tsx
  • https://github.com/software-mansion/react-native-screens/blob/main/src/native-stack/types.tsx
• Ensured that CI passes