chore: monorepo scaffolding

[graszka22]

What/Why?

Monorepo scaffolding:

• added packages/core, packages/android-enriched-markdown, packages/ios-enriched-markdown stubs
• moved src/, cpp/, android/ ios/ into packages/react-native-enriched-markdown (in a separate commit for easier review)
• updated paths
• fixed ci failure (probably too many changes caused too many arguments passed to cli command?)

The commands to build, lint, test, etc. stay the same.

Testing

• verified yarn, yarn prepare works
• verified example app builds on ios and android
• verified e2e tests start
• it would be good to confirm release still works

PR Checklist

• Code compiles and runs on iOS
• Code compiles and runs on Android
• Updated documentation/README if applicable
• Ran example app to verify changes
• E2E tests are passing
• Required E2E tests have been added (if applicable)

[hryhoriiK97]

LGTM!

I've verified locally:

• RN example app builds and runs on both iOS and Android
• Dry-run npm release works correctly with the new publishPath config