Add demo link to readme

Author: TRowbotham

README.md

@@ -9,6 +9,9 @@
 A [WHATWG URL](https://url.spec.whatwg.org/) spec compliant URL parser for working with URLs and their query strings.
 
 This API offers 2 objects that you can use to help you work with URLs; [URL](#url) and [URLSearchParams](#urlsearchparams).
+## Demo
+
+Checkout an interactive demo [here](https://url-demo.trowbotham.com/).
 
 ## Requirements