Add Unity post-processing build scripts for iOS and Android

[menstood]

Summary

This PR adds Unity post-processing build scripts for both iOS and Android platforms to automate the setup required for proper integration with the @azesmway/react-native-unity package.

✅ iOS:

• Reassigns the Data/ folder from the default Unity-iPhone target to the UnityFramework target
• Marks NativeCallProxy.h as a Public header in UnityFramework for external access via React Native

✅ Android:

• Removes all <intent-filter> blocks from AndroidManifest.xml in the Unity-generated unityLibrary to prevent duplicate launcher activity conflicts with the React Native host app

Notes

The scripts are placed in: unity/Editor/PostProcessBuild/ They run automatically when Unity builds for Android or iOS.