add Jekyll workflow for GitHub Pages deployment

.github/workflows/jekyll.yml

@@ -0,0 +1,80 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+# Sample workflow for building and deploying a Jekyll site to GitHub Pages
+
+name: Deploy Jekyll site to "_site" branch on GitHub Pages
+
+on:
+  # Runs on pushes targeting the default branch
+  push:
+    branches: ["main"]
+
+  # Allows you to run this workflow manually from the Actions tab
+  workflow_dispatch:
+
+# Sets permissions of the GITHUB_TOKEN to allow deployment to GitHub Pages
+permissions:
+  contents: write
+  pages: write
+  id-token: write
+
+# Allow only one concurrent deployment, skipping runs queued between the run in-progress and latest queued.
+# However, do NOT cancel in-progress runs as we want to allow these production deployments to complete.
+concurrency:
+  group: "pages"
+  cancel-in-progress: false
+
+jobs:
+  # Build job
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup Ruby
+        uses: ruby/setup-ruby@8575951200e472d5f2d95c625da0c7bec8217c42 # v1.161.0
+        with:
+          ruby-version: '3.1' # Not needed with a .ruby-version file
+          bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+          cache-version: 0 # Increment this number if you need to re-download cached gems
+      - name: Build with Jekyll
+        # Outputs to the './_site' directory by default
+        run: bundle exec jekyll build --baseurl "${{ steps.pages.outputs.base_path }}"
+        env:
+          JEKYLL_ENV: production
+
+  # Deployment job
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Checkout main branch
+        uses: actions/checkout@v4
+        with:
+          ref: 'main'
+      - name: Copy _site contents
+        run: |
+          cp -r _site/ Gemfile _config.yml /tmp/
+          git checkout -b _site
+          rm -rf *
+          cp -r /tmp/_site/* /tmp/Gemfile /tmp/_config.yml ./
+          git add --all
+          git config user.name github-actions
+          git config user.email [email protected]
+          git commit -m "update _site content"
+          git push --force origin _site
+      - name: Deploy to GitHub Pages
+        uses: jeffreytse/[email protected]
+        with:
+          provider: 'github'
+          token: ${{ secrets.GITHUB_TOKEN }}
+          repository: ''
+          branch: '_site'
+          jekyll_src: './'
+          jekyll_cfg: '_config.yml'