add github action for jekyll build

.github/workflows/github-pages.yml

@@ -0,0 +1,21 @@
+name: Build site for Deployment to blog.oxrud.com
+
+on:
+  push:
+    branches: [main]
+
+jobs:
+  build:
+    runs-on: ubuntu-22.04
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Setup Ruby and install gem dependencies
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: 3.2
+          bundler-cache: true
+
+      - name: Build site
+        run: jekyll build