Enable ci concurrency limits (#2)

Author: rzblue

.github/workflows/main.yml

@@ -2,6 +2,10 @@ name: CI
 
 on: [push, pull_request, workflow_dispatch]
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.ref }}
+  cancel-in-progress: true
+
 jobs:
   build:
     name: "Build and Test"