ci(build): restore on: push/PR/dispatch (keep concurrency)

Author: CoderDeltaLAN

.github/workflows/build.yml

@@ -1,11 +1,12 @@
-name: CI / build
-
 on:
   push:
     branches: [main]
   pull_request:
     branches: [main]
   workflow_dispatch:
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 jobs:
   build:
     name: build (${{ matrix.python-version }})