Add codegenConfig to package.json to prevent generating duplicate classes

[j-piasecki]

It seems like codegen will generate duplicated files if codegenConfig property is missing from package.json (meaning all view manager delegates and interfaces will be also generated under react-native-mmkv/android/build/generated/source/codegen/react/viewmanagers). This results in the build failing due to multiple definitions of the same classes.

I'm not exactly sure what jsSrcsDir should point to in this case. It doesn't really matter as long as the library doesn't depend on the generated code, but if it points to a non-existent directory the build will fail. Since files under src aren't included in the npm package, I figured the lib/module will do. Feel free to change it if you have other ideas.

Related issue: software-mansion/react-native-gesture-handler#2382

[mrousavy]

Thank you! 🖤