Fix gh action permission (#765)

Recent commit 21455f2 restricted gh action permissions to read only,
however, it needs package write permissions to update container images.

Signed-off-by: Marcus Brandenburger <bur@zurich.ibm.com>

Author: mbrandenburger

.github/workflows/test.yml

@@ -16,6 +16,7 @@ on:
 
 permissions:
   contents: read
+  packages: write
 
 env:
   DOCKER_REGISTRY: 'ghcr.io'