ENH: Add a GHA workflow file to build site on PRs (#22)

Add a GHA workflow file to build the site when opening pull requests.

Add the deployment status badge to the `README` file.

.github/workflows/build_site.yaml

@@ -0,0 +1,37 @@
+name: Build Jekyll site
+
+on:
+  push:
+    branches: ['main']
+  pull_request:
+    branches: ['main']
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+jobs:
+
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Pages
+        uses: actions/configure-pages@v3
+      - name: Build
+        uses: actions/jekyll-build-pages@v1
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v2
+
+  deploy:
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v2
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}

README.md

@@ -1,4 +1,10 @@
 # slicerdmri.github.io
+
+ [![][deployment-img]][deployment-link]
+
+[deployment-img]: https://github.com/SlicerDMRI/slicerdmri.github.io/actions/workflows/pages/pages-build-deployment/badge.svg
+[deployment-link]: https://dmri.slicer.org/
+
 SlicerDMRI organization website repository
 
 # Build