Define concurency group & drop permissions to read-all

Author: atodorov

.github/workflows/testing.yml

@@ -5,6 +5,12 @@ on:
     branches: master
   pull_request:
 
+concurrency:
+  group: ${{ github.ref }}-${{ github.workflow }}
+  cancel-in-progress: true
+
+permissions: read-all
+
 jobs:
   build-package:
     runs-on: ubuntu-latest