Add explicit read-only permissions to CI workflow (#316)

Author: arpitjain099

.github/workflows/ci.yml

@@ -25,6 +25,9 @@ on:
     branches:
       - main
 
+permissions:
+  contents: read
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}-${{ github.event_name }}
   cancel-in-progress: true