chore: Clean up root directory (#236)

* Clean up root

* remove unused REA patches

* Remove `cpp/` and create headers per platform

* fix `#import`

* fix `VISION_CAMERA_DISABLE_FRAME_PROCESSORS`

example/patches/react-native-reanimated+2.2.0.patch

@@ -1,20 +0,0 @@
-diff --git a/node_modules/react-native-reanimated/android/build.gradle b/node_modules/react-native-reanimated/android/build.gradle
-index bb707e7..9186873 100644
---- a/node_modules/react-native-reanimated/android/build.gradle
-+++ b/node_modules/react-native-reanimated/android/build.gradle
-@@ -7,8 +7,12 @@ def reactNativeVersion = json.version as String
- def (major, minor, patch) = reactNativeVersion.tokenize('.')
- 
- def engine = "jsc"
--if (project(':app').ext.react.enableHermes) {
--    engine = "hermes"
--}
-+rootProject.getSubprojects().forEach({project ->
-+     if (project.plugins.hasPlugin("com.android.application")) {
-+         if(project.ext.react.enableHermes) {
-+             engine = "hermes"
-+         }
-+     }
-+ })
- 
- artifacts.add("default", file("react-native-reanimated-${minor}-${engine}.aar"))