Add GitHub actions to automate image generation

Help reviewing pull requests by verify that the image builds and
streamline publishing images from releases.

.github/workflows/publish-docker-image.yml

@@ -0,0 +1,43 @@
+name: Publish Docker Image
+
+on:
+  release:
+    types: [ published ]
+
+env:
+  # GitHub repository is basically "$org/$repo"
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push-image:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v2
+
+    # User triggering the action is authenticated to the container registry
+    - name: Log in to the Container registry
+      uses: docker/login-action@v1.10.0
+      with:
+        registry: ghcr.io
+        username: ${{ github.actor }}
+        password: ${{ secrets.GITHUB_TOKEN }}
+
+    # Basically sets the image tag from the release
+    - name: Extract metadata for Docker
+      id: meta
+      uses: docker/metadata-action@v3.6.0
+      with:
+        images: ghcr.io/${{ env.IMAGE_NAME }}
+
+    - name: Build and push Docker image
+      uses: docker/build-push-action@v2.7.0
+      with:
+        context: .
+        push: true
+        tags: ${{ steps.meta.outputs.tags }}
+        labels: ${{ steps.meta.outputs.labels }}

.github/workflows/try-build-docker-image.yml

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+name: Build Docker image.
+
+on:
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Build the Docker image
+        run: docker build . --file Dockerfile