add: pull request page preview

.github/workflows/preview.yml

@@ -0,0 +1,45 @@
+name: Preview
+
+on:
+  pull_request:
+    types: [opened, synchronize, reopened, closed]
+
+concurrency: preview-${{ github.ref }}
+
+jobs:
+  preview:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+
+      - name: Checkout mdbook
+        uses: peaceiris/actions-mdbook@v2
+        with:
+          mdbook-version: "latest"
+      - name: Build mdbook
+        run: mdbook build --dest-dir out
+
+      - name: Cache Cargo registry and Cargo bin
+        id: cargo-cache
+        uses: actions/cache@v5
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            ~/.cargo/bin
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock','**/Cargo.toml') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Install mdbook-utils
+        if: steps.cargo-cache.outputs.cache-hit != 'true'
+        run: cargo install mdbook-utils
+
+      - name: Generate sitemap
+        run: mdbook-utils sitemap -o out/sitemap.xml -b https://rsdocsjp.org/ -y
+
+      - name: Deploy preview
+        uses: rossjrw/pr-preview-action@v1
+        with:
+          source-dir: ./out/