chore(sfc-playground): add pnpm usage to download template (#7815)

Author: godxiaoji

packages/sfc-playground/src/download/template/README.md

@@ -1,6 +1,6 @@
 # Vite Vue Starter
 
-This is a project template using [Vite](https://vitejs.dev/). It requires [Node.js](https://nodejs.org) version 18+, 20+.
+This is a project template using [Vite](https://vitejs.dev/). It requires [Node.js](https://nodejs.org) version 18+ or 20+.
 
 To start:
 
@@ -11,4 +11,8 @@ npm run dev
 # if using yarn:
 yarn
 yarn dev
+
+# if using pnpm:
+pnpm install
+pnpm run dev
 ```