ci: set ghcr write permissions explicitely for dependabot PRs (#2241)

.github/workflows/docker.yml

@@ -13,6 +13,9 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
   cancel-in-progress: true
 
+permissions:
+  packages: write
+
 jobs:
   build_and_push:
     runs-on: ubuntu-latest