Add concurrency limit to CI

Author: blink1073

.github/workflows/test.yml

@@ -2,6 +2,10 @@ name: Test
 
 on: [push, pull_request]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.sha }}
+  cancel-in-progress: true
+
 jobs:
   build:
     name: ${{ matrix.noxenv }}