docs(create-app): add pnpm commands (#3433)

Author: milahu

packages/create-app/README.md

@@ -17,6 +17,12 @@ With Yarn:
 $ yarn create @vitejs/app
 ```
 
+With PNPM:
+
+```bash
+$ pnpx @vitejs/create-app
+```
+
 Then follow the prompts!
 
 You can also directly specify the project name and the template you want to use via additional command line options. For example, to scaffold a Vite + Vue project, run:
@@ -30,6 +36,9 @@ npm init @vitejs/app my-vue-app -- --template vue
 
 # yarn
 yarn create @vitejs/app my-vue-app --template vue
+
+# pnpm
+pnpx @vitejs/create-app my-vue-app --template vue
 ```
 
 Currently supported template presets include: