chore: replace base64url with b64u (#179)

Author: panva

lib/util/base64url.js

@@ -5,7 +5,12 @@
  */
 "use strict";
 
-var impl = require("base64url");
+var impl = require("b64u");
+
+// webpack specific
+if (impl.default) {
+  impl = impl.default;
+}
 
 /**
  * @namespace base64url