Improve readme warning (#379)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

readme.md

@@ -44,7 +44,8 @@
 npm install query-string
 ```
 
-**Not `npm install querystring`!!!!!**
+> [!WARNING]
+> Remember the hyphen! Do not install the deprecated [`querystring`](https://github.com/Gozala/querystring) package!
 
 For browser usage, this package targets the latest version of Chrome, Firefox, and Safari.