Use GHCR token fallback for registry login

.github/workflows/docker-publish.yml

@@ -36,7 +36,7 @@ jobs:
         with:
           registry: ${{ env.REGISTRY }}
           username: ${{ github.repository_owner }}
-          password: ${{ secrets.GITHUB_TOKEN }}
+          password: ${{ secrets.GHCR_TOKEN || secrets.GITHUB_TOKEN }}
 
       - name: Extract metadata
         id: meta