add CI for pull requests

.github/workflows/actions.yml

@@ -0,0 +1,17 @@
+name: Build website
+
+on:
+    pull_request: 
+
+jobs:
+    build:
+        runs-on: ubuntu-latest
+        steps:
+        - name: Checkout
+          uses: actions/checkout@v4
+        - name: Build
+          uses: actions/jekyll-build-pages@v1
+        - name: Upload artifact
+          uses: actions/upload-artifact@v4
+          with:
+            path: ./_site