Add workflow concurrency check (#1630)

Add concurrency check, new workflows triggered on the same branch should
cancel old ones in progress.
#1619

.github/workflows/on-pr.yml

@@ -5,6 +5,10 @@ on:
   pull_request:
     branches: [ "main" ]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   pre-commit:
     uses: ./.github/workflows/pre-commit.yml