Add GitHub Pages deployment action

Author: kateinoigakukun

.github/workflows/docs.yml

@@ -0,0 +1,49 @@
+name: Deploy RDoc site to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow one concurrent deployment
+concurrency:
+  group: "pages"
+  cancel-in-progress: true
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    env:
+      HUGO_VERSION: 0.102.3
+    steps:
+      - uses: actions/checkout@v3
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.1'
+          bundler-cache: true
+      - name: Setup Pages
+        id: pages
+        uses: actions/configure-pages@v2
+      - name: Build HTML by RDoc
+        run: rake rdoc
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v1
+        with:
+          path: ./html
+
+  deploy:
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v1
+