Update build.yml to trigger on PRs

.github/workflows/build.yml

@@ -2,9 +2,16 @@ name: Build Eleventy
 
 on:
   push:
+    paths-ignore:
+      - '/maintenance/**'
+      - '/README.md'
     branches:
       - main
   workflow_dispatch:
+  pull_request:
+    paths-ignore:
+      - '/maintenance/**'
+      - '/README.md'
 
 permissions:
   contents: write
@@ -34,4 +41,4 @@ jobs:
         uses: peaceiris/actions-gh-pages@v4
         with:
           publish_dir: ./docs
-          github_token: ${{ secrets.GITHUB_TOKEN }}
+          github_token: ${{ secrets.GITHUB_TOKEN }}