chore: enable CI build on fork pull requests

Author: sgarner

.github/workflows/build.yml

@@ -1,6 +1,10 @@
 name: Build
 
-on: [ push ]
+on:
+  push:
+    branches: [ '**' ]
+  pull_request:
+    branches: [ '**' ]
 
 jobs:
   #