docs: Add new section for google/docsy

An example workflow for autoprefixer, postcss-cli,
and a Hugo theme which has recursive Git submodules

https://github.com/peaceiris/actions-hugo/issues/340
https://github.com/google/docsy-example/issues/60

README.md

@@ -82,7 +82,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
         with:
-          submodules: true  # Fetch Hugo themes
+          submodules: true  # Fetch Hugo themes (true OR recursive)
           fetch-depth: 0    # Fetch all history for .GitInfo and .Lastmod
 
       - name: Setup Hugo
@@ -192,6 +192,60 @@ The alpine base Hugo Docker image is provided on the following repository.
 
 > [peaceiris/hugo-extended-docker: Hugo alpine base Docker image (Hugo extended and Hugo Modules)](https://github.com/peaceiris/hugo-extended-docker)
 
+### ⭐️ Workflow for autoprefixer and postcss-cli
+
+Here is an example workflow for the [google/docsy] Hugo theme.
+This theme needs `autoprefixer` and `postcss-cli` to build a project.
+The following workflow is tested on [google/docsy-example].
+
+[google/docsy]: https://github.com/google/docsy
+[google/docsy-example]: https://github.com/google/docsy-example
+
+```yaml
+name: github pages
+
+on:
+  push:
+    branches:
+      - master
+
+jobs:
+  deploy:
+    runs-on: ubuntu-18.04
+    steps:
+      - uses: actions/checkout@v2
+        with:
+          submodules: recursive  # Fetch the Docsy theme
+          fetch-depth: 0         # Fetch all history for .GitInfo and .Lastmod
+
+      - name: Setup Hugo
+        uses: peaceiris/actions-hugo@v2
+        with:
+          hugo-version: '0.71.0'
+          extended: true
+
+      - name: Setup Node
+        uses: actions/setup-node@v1
+        with:
+          node-version: '12.x'
+
+      - name: Cache dependencies
+        uses: actions/cache@v1
+        with:
+          path: ~/.npm
+          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+
+      - run: npm ci
+      - run: hugo --minify
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+```
+
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