add another reference to RFC 2898

Author: karimhamdanali

swift/ql/src/queries/Security/CWE-259/ConstantPassword.qhelp

@@ -17,5 +17,6 @@
 
   <references>
     <li><a href="https://www.okta.com/blog/2019/03/what-are-salted-passwords-and-password-hashing/">What are Salted Passwords and Password Hashing?</a></li>
+    <li><a href="https://www.rfc-editor.org/rfc/rfc2898">Password-Based Cryptography Specification</a></li>
   </references>
 </qhelp>