added cosign to the container build

.github/workflows/publish_to_pypi_and_build_container.yml

@@ -124,6 +124,9 @@ jobs:
         with: 
           submodules: 'true'
 
+      - name: Install Cosign
+        uses: sigstore/cosign-installer@v3.7.0
+
       # Workaround: https://github.com/docker/build-push-action/issues/461
       - name: Setup Docker buildx
         uses: docker/setup-buildx-action@v3
@@ -158,6 +161,13 @@ jobs:
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
 
+      - name: Sign image with a key
+        run: |
+          cosign sign --yes --key env://COSIGN_PRIVATE_KEY ${{ env.REGISTRY }}/${{ github.actor }}/${{ env.IMAGE_NAME }}:${{ github.ref_name }}
+        env:
+          COSIGN_PRIVATE_KEY: ${{ secrets.COSIGN_PRIVATE_KEY }}
+          COSIGN_PASSWORD: ${{ secrets.COSIGN_PASSWORD }}
+
 
   # publish-to-testpypi:
   #   name: Publish Python 🐍 distribution 📦 to TestPyPI