Fix minor typo in a comment.

Author: everett1992

lib/Server.js

@@ -192,7 +192,7 @@ function Server(compiler, options) {
 		}.bind(this),
 
 		middleware: function() {
-			// include our middleware to ensure it is able to handle '/index.html' requrst after redirect
+			// include our middleware to ensure it is able to handle '/index.html' request after redirect
 			app.use(this.middleware);
 		}.bind(this),