docs: document array and multiple-args support in req.is (#2042)

Author: GauravKesh

_includes/api/en/4x/req-is.md

@@ -21,8 +21,22 @@ req.is('application/json')
 req.is('application/*')
 // => 'application/*'
 
+// Using arrays
+// When Content-Type is application/json
+req.is(['json', 'html'])
+// => 'json'
+
+// Using multiple arguments
+// When Content-Type is application/json
+req.is('json', 'html')
+// => 'json'
+
 req.is('html')
 // => false
+req.is(['xml', 'yaml'])
+// => false
+req.is('xml', 'yaml')
+// => false
 ```
 
-For more information, or if you have issues or concerns, see [type-is](https://github.com/expressjs/type-is).
+For more information, or if you have issues or concerns, see [type-is](https://github.com/expressjs/type-is).

_includes/api/en/5x/req-is.md

@@ -15,8 +15,17 @@ req.is('json') // => 'json'
 req.is('application/json') // => 'application/json'
 req.is('application/*') // => 'application/*'
 
-req.is('html')
-// => false
+// Using arrays
+// When Content-Type is application/json
+req.is(['json', 'html']) // => 'json'
+
+// Using multiple arguments
+// When Content-Type is application/json
+req.is('json', 'html') // => 'json'
+
+req.is('html') // => false
+req.is(['xml', 'yaml']) // => false
+req.is('xml', 'yaml') // => false
 ```
 
 For more information, or if you have issues or concerns, see [type-is](https://github.com/expressjs/type-is).