Prevent duplicate CI Build runs for PR commits (#99)

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: danielchalmers <[email protected]>

.github/workflows/build.yml

@@ -2,6 +2,7 @@ name: Build
 
 on:
   push:
+    branches: [ master ]
   pull_request:
 
 jobs: