ci: add least-privilege permissions block

Author: nunomaduro

.github/workflows/tests.yml

@@ -2,6 +2,9 @@ name: Tests
 
 on: ['push', 'pull_request']
 
+permissions:
+  contents: read
+
 jobs:
   ci:
     runs-on: ${{ matrix.os }}
@@ -38,4 +41,4 @@ jobs:
         composer-options: "--prefer-dist"
 
     - name: Unit Tests
-      run: vendor/bin/pest --colors=always
+      run: vendor/bin/pest --colors=always