Add issue marker for normative references for vocabulary files.

index.html

@@ -5214,6 +5214,14 @@ <h3>Vocabularies</h3>
 location under W3C control.
         </p>
 
+        <p class="issue" title="How to normatively refer to vocabulary files">
+The Working Group is currently discussing how it might want to normatively
+refer to the vocabulary files that are under the control of the Working Group.
+Current options are: inclusion of the files directly into the specification or
+publishing the files in W3C TR space and referring to them by using a
+cryptographic hash.
+        </p>
+
       </section>
       <section class="informative">
         <h3>Differences between Contexts, Types, and CredentialSchemas</h3>