add artifact upload

Author: vomba

.github/workflows/build-openstack-capi-image.yml

@@ -77,3 +77,9 @@ jobs:
         run: make build-qemu-ubuntu-2404-efi
         env:
           PACKER_VAR_FILES: kubernetes.json
+
+      - name: store openstack image
+        uses: actions/upload-artifact@v4
+        with:
+          name: openstack-image
+          path: ./output/