Add paragraph on trust lists.

index.html

@@ -2852,6 +2852,19 @@ <h3>Trust Model</h3>
           </li>
         </ul>
 
+       <p>
+How [=verifiers=] decide which [=issuers=] to trust, and for what data or
+purposes, is out of scope for this recommendation. Some [=issuers=] (such as
+well-known organizations), might be trusted by many [=verifiers=] simply because
+of their reputation. Some [=issuers=] and [=verifiers=] might be members of a
+community in which all members trust each other due to the rules of membership.
+Some [=verifiers=] might trust a specific trust-service provider whose
+responsibility is to vet [=issuers=] and list them in a trust list such as those
+specified in [[[ETSI-TRUST-LISTS]]] [[?ETSI-TRUST-LISTS]] or the
+<a href="https://helpx.adobe.com/acrobat/kb/approved-trust-list1.html">Adobe
+Approved Trust List</a>.
+        </p>
+
         <p>
 By decoupling the expectations between the [=issuer=] and the [=verifier=],
 a more flexible and dynamic trust model is created, such that market