docs(configuration): update static.publicPath type (#5306)

Author: snitin315

src/content/configuration/dev-server.mdx

@@ -1227,7 +1227,7 @@ module.exports = {
 
 ### publicPath
 
-`string = '/'` `string`
+`string = '/'` `[string]`
 
 Tell the server at which URL to serve [`static.directory`](#directory) content. For example to serve a file `assets/manifest.json` at `/serve-public-path-url/manifest.json`, your configurations should be as following: