Add issue marker for TBD Appendix.

index.html

@@ -1026,7 +1026,7 @@ <h3>Workflows and Exchanges</h3>
 credential offer, or as the "client_id" of an OID4VP authorization request,
 indicating that OID4VCI or OID4VP, respectively, ought to be used. This section
 focuses on how an exchange client uses VC API to interact with the exchange;
-see appendix __** fill me in! **__ to see how to combine VC API exchanges with other protocols
+see <span class="issue">Appendix TBD</span> to see how to combine VC API exchanges with other protocols
 such as OID4VCI, OID4VP, and DIDComm.
       </p>
       <p>