Add GitHub Actions workflow for automatic image creation (#4)

Signed-off-by: Aitor Iturrioz <aiturrioz@tknika.eus>

.github/workflows/build-and-push.yaml

@@ -0,0 +1,44 @@
+name: Build and push to GitHub Container Registry
+
+on:
+  workflow_dispatch:
+  push:
+    tags:
+      - 'v*.*.*'
+
+permissions: 
+  packages: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v3
+      - name: Login to GHCR
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Docker meta
+        id: image_metadata
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+          tags: |
+            type=semver,pattern={{version}}
+            type=sha
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          push: true
+          platforms: linux/amd64,linux/arm/v7,linux/arm64,linux/arm/v8
+          tags: ${{ steps.image_metadata.outputs.tags }}
+          labels: ${{ steps.image_metadata.outputs.labels }}