docs(express.json): clarify usage and add route-specific limit example

_includes/api/en/4x/express.json.md

@@ -39,4 +39,13 @@ The following table describes the properties of the optional `options` object.
 | `type`        | This is used to determine what media type the middleware will parse. This option can be a string, array of strings, or a function. If not a function, `type` option is passed directly to the [type-is](https://www.npmjs.org/package/type-is#readme) library and this can be an extension name (like `json`), a mime type (like `application/json`), or a mime type with a wildcard (like `*/*` or `*/json`). If a function, the `type` option is called as `fn(req)` and the request is parsed if it returns a truthy value. | Mixed | `"application/json"` |
 | `verify`      | This option, if supplied, is called as `verify(req, res, buf, encoding)`, where `buf` is a `Buffer` of the raw request body and `encoding` is the encoding of the request. The parsing can be aborted by throwing an error. | Function | `undefined` |
 
-</div>
+</div>
+
+#### Example: Different limits for specific routes
+
+```js
+// Limit 5MB for /upload
+app.use('/upload', express.json({ limit: '5mb' }))
+
+// Default limit for other routes
+app.use(express.json())