fix: missing export (#217)

Co-authored-by: David Patrick <david.patrick@auth0.com>

Author: charsleysa

src/index.js

@@ -9,6 +9,7 @@ import { passportJwtSecret } from './integrations/passport';
 module.exports = (options) => {
   return new JwksClient(options);
 };
+module.exports.JwksClient = JwksClient;
 
 module.exports.ArgumentError = errors.ArgumentError;
 module.exports.JwksError = errors.JwksError;