Publish docker images (#2130)

Publish docker images for master branch with tag `latest`

.github/workflows/docker-image.yml

@@ -0,0 +1,27 @@
+name: Docker Image CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: docker login
+      uses: docker/login-action@v1
+      with:
+        username: ${{ secrets.DOCKER_USER }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+    
+    - name: build the Docker image
+      run: docker build -t acinq/eclair .
+      
+    - name: docker push
+      run: docker push acinq/eclair