Android Docker Image for react native

Motivation

This is an implementation of https://github.com/react-native-community/discussions-and-proposals/blob/master/proposals/0036-Official-Docker.md.

Showcase

https://github.com/react-native-community/ci-sample

Dockerhub Image

see https://hub.docker.com/r/reactnativecommunity/react-native-android/

The image preloads the Gradle Wrapper distribution selected by the GRADLE_VERSION build argument. Its wrapper cache is stored in GRADLE_USER_HOME=/opt/gradle-home, so ./gradlew can start without downloading Gradle in ephemeral CI containers.

Original version is split from react-native repo, see https://github.com/facebook/react-native/blob/988366a4179d87d667e5d9396efdfba4cbbe0b2e/ContainerShip/Dockerfile.android-base.