feat: Push to github container registry too

.github/workflows/dotnet.yml

@@ -56,12 +56,20 @@ jobs:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
       - name: Extract metadata (tags, labels) for Docker
         id: meta
         uses: docker/metadata-action@v5
         with:
           images: |
             ${{ env.DOCKER_IMAGE }}
+            ghcr.io/${{ github.repository }}
 
       - name: Build and push
         uses: docker/build-push-action@v5