Add GitHub Actions workflow for documentation

.github/workflows/docs.yml

@@ -0,0 +1,40 @@
+name: Build and Deploy Docs
+
+on:
+  push:
+    branches:
+      - gh-pages
+    paths:
+      - 'docs/**'
+      - '_config.yml'
+      - 'index.md'
+      - '.github/workflows/docs.yml'
+
+jobs:
+  build-and-deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Setup Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.1'
+          bundler-cache: true
+
+      - name: Install dependencies
+        run: |
+          gem install bundler
+          bundle init
+          bundle add jekyll
+          bundle add just-the-docs
+
+      - name: Build site
+        run: bundle exec jekyll build
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./_site