👷 Build + publish Docker container on release

Adds an action to build and publish the Docker container to the GitHub container registry after each release.

.github/workflows/docker-release.yml

@@ -0,0 +1,40 @@
+# Test and build the Docker container after a release
+# Then push it to GH container registry if all checks pass
+name: Build & Publish Docker Image
+on:
+  release:
+    types: [published]
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+jobs:
+  build-and-push-image:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      # Get the code
+      - name: Checkout repository 🛎️
+        uses: actions/checkout@v2
+      # Log into ghcr.io
+      - name: Log in to the Container registry 🔑
+        uses: docker/login-action@f054a8b539a109f9f41c372932f1ae047eff08c9
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      # Get release version, for Docker tag
+      - name: Extract metadata (tags, labels) for Docker 🗂️
+        id: meta
+        uses: docker/metadata-action@98669ae865ea3cffbcbaa878cf57c20bbf1c6c38
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+      # Build the container, and push if succesful
+      - name: Build and push Docker image ⚒️
+        uses: docker/build-push-action@ad44023a93711e3deb337508980b4b5e9bcdc5dc
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}