Add dark mode and publish to GitHub Pages using GitHub Actions

.github/workflows/publish.yml

@@ -0,0 +1,33 @@
+name: Publish to GitHub Pages
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+
+      - name: Set up Ruby
+        uses: actions/setup-ruby@v1
+        with:
+          ruby-version: '2.7'
+
+      - name: Install dependencies
+        run: |
+          gem install bundler
+          bundle install
+
+      - name: Build site
+        run: bundle exec jekyll build
+
+      - name: Deploy to GitHub Pages
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./_site