build: Set up Docker auto build with GH Actions

.dockerignore

@@ -3,8 +3,8 @@
 # Dockerfile.tsc will still be used.
 .env
 .git
+.github
 .gitignore
 .vscode
-post-checkout
 docker-compose*
 Dockerfile*

.github/workflows/deploy.yml

@@ -0,0 +1,37 @@
+name: Build and deploy Docker image
+
+on:
+  push:
+    branches:
+      # WARNING: Change to production!
+      - docker
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GHCR
+        # WARNING: GHCR Personal Access Token expires! Recreate every 90 days.
+        run: echo "${{ secrets.GHCR_PAT }}" | docker login ghcr.io -u ${{ github.actor }} --password-stdin
+
+      - name: Build and tag Docker image
+        run: |
+          IMAGE_NAME=ghcr.io/${{ github.repository }}:${{ github.sha }}
+          docker buildx build -t $IMAGE_NAME .
+          docker tag $IMAGE_NAME ghcr.io/${{ github.repository }}:latest
+          echo "Image built: $IMAGE_NAME"
+
+      - name: Push Docker image to GHCR
+        run: |
+          IMAGE_NAME=ghcr.io/${{ github.repository }}:${{ github.sha }}
+          docker push $IMAGE_NAME
+          docker push ghcr.io/${{ github.repository }}:latest
+          echo "Image pushed: $IMAGE_NAME"
+