Add Docker GitHub workflow.

.github/workflows/docker.yml

@@ -0,0 +1,46 @@
+name: Docker image build
+
+on:
+  push:
+    branches:
+      - 'main'
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+      -
+        name: Check out the repo
+        uses: actions/checkout@v3
+      #-
+      #  name: Log in to DockerHub
+      #  uses: docker/login-action@v1
+      #  with:
+      #    username: ${{ secrets.DOCKERHUB_USERNAME }}
+      #    password: ${{ secrets.DOCKERHUB_TOKEN }}
+      - name: Log in to GitHub container registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: |
+            ghcr.io/${{ github.repository }}
+      -
+        name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}