Update README.md to fix HTTPResponseError (#1135)

In the 'Handling client and server errors', the class HTTPResponseError constructor has to call 'super()' before accessing 'this.response'

Not doing this throws the following exception: "ReferenceError: Must call super constructor in derived class before accessing 'this' or returning from derived constructor"

Fix: This just changes the order so super(...) is first, then this.response...

MDN Reference: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/super#using_super_in_classes

README.md

@@ -240,8 +240,8 @@ import fetch from 'node-fetch';
 
 class HTTPResponseError extends Error {
 	constructor(response, ...args) {
-		this.response = response;
 		super(`HTTP Error Response: ${response.status} ${response.statusText}`, ...args);
+		this.response = response;
 	}
 }