publish image on release (#85)

.github/workflows/build.yaml

 name: Build Docker image
 
-on: [push, pull_request]
+on:
+  push:
+    paths: 
+      - Dockerfile
+  pull_request:
+    paths: 
+      - Dockerfile
 
 jobs:
     build:

.github/workflows/publish.yml

-name: Publish Docker image
+name: Publish
 on:
-  push:
-    branches:
-      - master
   release:
     types: [published]
 
 jobs:
   push_to_registry:
     name: Push Docker image to Docker Hub
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-20.04
     steps:
       - name: Check out the repo
         uses: actions/checkout@v2
-      - name: Push to Docker Hub
-        uses: docker/build-push-action@v1
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Login to DockerHub
+        uses: docker/login-action@v1
         with:
           username: ${{ secrets.DOCKER_USERNAME }}
           password: ${{ secrets.DOCKER_PASSWORD }}
-          repository: reactnativecommunity/react-native-android
-          tag_with_ref: true
-          tags: latest
+
+      - name: Push to Docker Hub
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          tags: |
+            reactnativecommunity/react-native-android:latest
+            reactnativecommunity/react-native-android:${{ GITHUB_REF }}

README.md

 ## Android Docker Image for react native
-[![CircleCI](https://circleci.com/gh/react-native-community/docker-android.svg?style=svg)](https://circleci.com/gh/react-native-community/docker-android)
+[![Publish](https://github.com/react-native-community/docker-android/workflows/Publish/badge.svg?event=release)](https://hub.docker.com/r/reactnativecommunity/react-native-android) 
 [![Docker Pulls](https://img.shields.io/docker/pulls/reactnativecommunity/react-native-android.svg?maxAge=3600)](https://hub.docker.com/r/reactnativecommunity/react-native-android) 
 [![Docker Layers](https://images.microbadger.com/badges/image/reactnativecommunity/react-native-android.svg)](https://hub.docker.com/r/reactnativecommunity/react-native-android)