Set explicit permissions for GitHub Actions workflows (#432)

This change was made by an automated process to ensure all GitHub Actions workflows have explicitly defined permissions as per best practices.

Author: picatz

.github/workflows/ci.yml

@@ -5,6 +5,9 @@ on:
     branches:
       - main
 
+permissions:
+  contents: read
+
 jobs:
   build-and-test:
     runs-on: ubuntu-latest