chore: add pull_request to workflow

Author: skovy

.github/workflows/build.yml

@@ -1,8 +1,13 @@
 name: Build
 on:
   push:
+    branches:
+      - "master"
+      - "alpha"
+  pull_request:
     branches:
       - "**"
+
 jobs:
   release:
     name: Test and Release