Set explicit permissions for GitHub Actions workflows

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

@@ -1,5 +1,7 @@
 name: "Continuous Integration"
 on: [push, pull_request]
+permissions:
+  contents: read
 
 jobs:
   validation:
@@ -47,4 +49,4 @@ jobs:
       uses: gradle/actions/setup-gradle@v3
 
     - name: Run copyright and code format checks
-      run: ./gradlew --no-daemon spotlessCheck
+      run: ./gradlew --no-daemon spotlessCheck