ci: allow attestations in docker workflow

[skip ci]

Change-Id: I3b39c31bf721b3b3ebcd6c0405ce1cba77d15d38
diff --git a/.github/workflows/docker.yml b/.github/workflows/docker.yml
index 72eaefd..267e3f4 100644
--- a/.github/workflows/docker.yml
+++ b/.github/workflows/docker.yml
@@ -9,8 +9,9 @@
   workflow_dispatch:
 
 permissions:
-  packages: write
+  attestations: write
   id-token: write
+  packages: write
 
 jobs:
   ndn-cxx-build: