add pull request facilities similar to php repo

Author: GlenDC

.github/workflows/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,4 @@
+**Please do not submit any pull requests here – they will be closed!**
+
+This repository is a read-only subset of the Datastar monorepo. Please open your pull request there instead:
+<https://github.com/starfederation/datastar>

.github/workflows/close-pull-request.yml

@@ -0,0 +1,15 @@
+name: Close Pull Request
+
+on:
+  pull_request_target:
+    types: [opened]
+
+jobs:
+  run:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: superbrothers/close-pull-request@v3
+        with:
+          comment: |
+            Thanks for your contribution! This repository is a read-only subset of the Datastar monorepo. Please open your pull request there instead:
+            <https://github.com/starfederation/datastar>