docs: update for v3

peaceiris · peaceiris · commit b1aaa85b6766 · 2020-02-05T17:10:00.000+09:00
diff --git a/README.md b/README.md
@@ -602,7 +602,7 @@ jobs:
 
       - name: Deploy
         uses: peaceiris/actions-gh-pages@v3
-        env:
+        with:
           deploy_key: ${{ secrets.ACTIONS_DEPLOY_KEY }}
           publish_dir: ./out
 ```
