Share extension plugin for Expo#

This plugin handles moving the necessary files into their respective iOS and Android targets and updating the build phases, plists, manifests, etc.

Steps#

ios#

1. Update entitlements
2. Set the app group to group.
3. Add the extension plist
4. Add the view controller
5. Update the xcode project's build phases

android#

1. Update the manifest with the intents the app can receive

Credits#

Adapted from https://github.com/andrew-levy/react-native-safari-extension and https://github.com/timedtext/expo-config-plugin-ios-share-extension/blob/master/src/withShareExtensionXcodeTarget.ts