ci: add workflow to build the docker image

.github/workflows/docker.yml

@@ -0,0 +1,59 @@
+name: Docker build on main branch
+
+on:
+  push:
+    branches:
+      - main
+
+env:
+  DOCKER_REGISTRY: ghcr.io
+  DOCKER_IMAGE: vojtechmares/backoffice
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          ref: ${{ github.ref }}
+
+      # Setup Docker
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
+      - name: Docker login
+        uses: docker/login-action@v2
+        with:
+          registry: ${{ env.DOCKER_REGISTRY }}
+          # Use repository secrets for username and password, not organization secrets
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Docker meta
+        id: docker_meta
+        uses: docker/metadata-action@v4
+        with:
+          tags: |
+            type=schedule
+            type=ref,event=branch
+            type=ref,event=tag
+            type=ref,event=pr
+            type=sha,format=long
+            type=raw,value=${{ github.ref_name }}-${{ github.sha }}
+            type=raw,value=latest,enable=${{ github.ref == format('refs/heads/{0}', 'main') }}
+          images: |
+            ${{ env.DOCKER_REGISTRY }}/${{ env.DOCKER_IMAGE }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v4
+        with:
+          pull: true
+          push: true
+          tags: ${{ steps.docker_meta.outputs.tags }}
+          labels: ${{ steps.docker_meta.outputs.labels }}
+          # platforms: linux/amd64,linux/arm64,linux/arm/v7
+          cache-from: type=registry,ref=${{ env.DOCKER_REGISTRY }}/${{ env.DOCKER_IMAGE }}:latest