restrict GitHub Actions to master branch and add workflow_dispatch trigger

.github/workflows/githubci.yml

@@ -1,13 +1,18 @@
 name: Build
 
 on:
+  workflow_dispatch:
   pull_request:
   push:
-  repository_dispatch:
+    branches: [ master ]
   release:
     types:
       - created
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   set-matrix:
     runs-on: ubuntu-latest