Fix typo.

README.md

@@ -456,7 +456,7 @@ img1, img2, img3, img4
 var source = "<strong>hello</strong><script>alert(/xss/);</script>end";
 var html = xss(source, {
   whiteList: [], // empty, means filter out all tags
-  stripIgnoreTag: true, // filter out all HTML not in the whilelist
+  stripIgnoreTag: true, // filter out all HTML not in the whitelist
   stripIgnoreTagBody: ["script"] // the script tag is a special case, we need
   // to filter out its content
 });