Meta: Limit auto-rendering to primary branch(es)

Author: gibson042

.github/workflows/build.yml

@@ -1,6 +1,10 @@
 name: Deploy spec
 
-on: [push]
+on:
+  push:
+    branches:
+    - main
+    - master
 
 jobs:
   build:
@@ -16,4 +20,4 @@ jobs:
     - name: commit changes
       uses: elstudio/actions-js-build/commit@v3
       with:
-        commitMessage: "fixup: [spec] `npm run build`"
+        commitMessage: "fixup: [spec] `npm run build`"