docs: mention @types/node and @types/fs-extra requirements (google#1134)

Author: antongolub

docs/setup.md

@@ -58,7 +58,11 @@ import { $ } from 'zx'
 const { $ } = require('zx')
 ```
 
-It has also built-in TypeScript libdefs.
+It has also built-in TypeScript libdefs. But `@types/fs-extra` and `@types/node` are required to be installed on user's side.
+
+```bash
+npm i -D @types/fs-extra @types/node
+```
 
 ```ts
 import { type Options } from 'zx'