chore(cicd): Only run on pr and push to main

Codex- · Codex- · commit f15f952d412e · 2023-07-25T13:19:32.000+12:00
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
@@ -1,6 +1,9 @@
 name: build
 on:
+  pull_request:
   push:
+    branches:
+      - main
 
 jobs:
   build:
