Potential fix for code scanning alert no. 2: Workflow does not contain permissions

Co-authored-by: Copilot Autofix powered by AI <62310815+github-advanced-security[bot]@users.noreply.github.com>

Author: zhaochunqi

.github/workflows/ci.yml

@@ -7,6 +7,9 @@ on:
     branches:
       - main
 
+permissions:
+  contents: read
+
 jobs:
   test_and_coverage:
     runs-on: ubuntu-latest