Add fabric on Android

[okwasniewski]

Summary:

• Configure gradle files
• Implement / extend the generated native interfaces
• Ensure backwards compatibility by splitting implementations into two folders.

Used examples / references:

• React native slider implementation

Test Plan:

• Setup fabric example to test the app using RN 0.70 RC

Test plan for RN <0.70:

1. Set newArchEnabled to true inside example/android/gradle.properties
2. Add this line in example/android/app/src/main/jni/Android.mk file.

+ include $(NODE_MODULES_DIR)/@react-native-community/slider/android/build/generated/source/codegen/jni/Android.mk
include $(CLEAR_VARS)

In the same file above, go to the LOCAL_SHARED_LIBRARIES setting and add the following line:

 libreact_codegen_rncore \
+ libreact_codegen_ReactSlider \
libreact_debug \

3. Update example/android/app/src/main/jni/MainComponentsRegistry.cpp

#include <react/renderer/components/rncore/ComponentDescriptors.h>+ #include <react/renderer/components/ReactSlider/ComponentDescriptors.h>
...
MainComponentsRegistry::sharedProviderRegistry() {
auto providerRegistry = CoreComponentsRegistry::sharedProviderRegistry();
// Custom Fabric Components go here. You can register custom
// components coming from your App or from 3rd party libraries here.
//
// providerRegistry->add(concreteComponentDescriptorProvider<
// AocViewerComponentDescriptor>());
+ providerRegistry->add(concreteComponentDescriptorProvider<RNCSliderComponentDescriptor>());
return providerRegistry;
}

Then, to launch the project run:

npm run install && npm run example-android

[okwasniewski]

This PR is part of #380 - linking this to the issue.

[BartoszKlonowski]

I left some very minor comments, but it's totally well done!
Thank you! 👍

[BartoszKlonowski]

👍