Update CI workflow for master branch and concurrency

Author: MakD

.github/workflows/ci.yml

@@ -2,11 +2,13 @@ name: CI
 
 on:
   push:
+    branches: [master]
   pull_request:
+  workflow_dispatch:
 
 concurrency:
-  group: ci-${{ github.ref }}
-  cancel-in-progress: true
+  group: ci-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: ${{ github.event_name == 'pull_request' }}
 
 permissions:
   contents: read