Update webauthn-2021.html

This PR adds an item to the proposed charter to make it clear that we hope to work on items related to w3c/webauthn#1637.

2021/webauthn-2021.html

@@ -166,6 +166,7 @@ <h2>Scope</h2>
 		  <li> Dynamic linking of authentication credentials; 
 		  <li> Storing of private key(s); 
 		  <li> Account recovery and/or credential backup options.
+		  <li> Facilitate relying party adoption through additional API enhancements such as returning transport indications in assertions, a credential &ldquo;durability&rdquo; signal, and credential status feedback signaling from relying parties.
 		  </ol>
     </p><p>
     Dependencies may exist on