README: Tweak require instructions

Author: mathiasbynens

README.md

@@ -25,6 +25,10 @@ npm install string.prototype.codepointat
 Then, in [Node.js](http://nodejs.org/):
 
 ```js
+require('string.prototype.codepointat');
+
+// On Windows and on Mac systems with default settings, case doesn’t matter,
+// which allows you to do this instead:
 require('String.prototype.codePointAt');
 ```