ci: add least-privilege permissions block

Author: nunomaduro

.github/workflows/ci.yml

@@ -2,6 +2,9 @@ name: Continuous Integration
 
 on: ['push', 'pull_request']
 
+permissions:
+  contents: read
+
 jobs:
   ci:
     runs-on: ubuntu-latest
@@ -41,5 +44,4 @@ jobs:
       run: vendor/bin/phpstan analyse
 
     - name: PHPUnit Testing
-      run: vendor/bin/phpunit --coverage-text --coverage-clover=coverage.xml
-
+      run: vendor/bin/phpunit --coverage-text --coverage-clover=coverage.xml