Publish docker image to GHCR (#644)

refs developmentseed/osmcha-migration-internal#3

.github/workflows/docker-publish.yml

@@ -0,0 +1,35 @@
+name: Build Docker Image, Push to GHCR
+
+on:
+  push:
+    branches:
+    - master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    - name: Set up Docker Buildx
+      uses: docker/setup-buildx-action@v1
+
+    - name: Login to GitHub Container Registry
+      uses: docker/login-action@v2
+      with:
+        registry: ghcr.io
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+
+    - name: Build and push Docker image
+      uses: docker/build-push-action@v4
+      with:
+        context: ./compose/django
+        push: true
+        tags: |
+          ghcr.io/willemarcel/osmcha-django:latest
+          ghcr.io/willemarcel/osmcha-django:${{ github.sha }}
+        cache-from: type=gha
+        cache-to: type=gha,mode=max