i18n improvements: properly link UTF-8 term.

Co-authored-by: Addison Phillips <[email protected]>

Author: Wind4Greg

index.html

@@ -1244,7 +1244,7 @@ <h4>Base Proof Serialization (bbs-2023)</h4>
             </li>
             <li>
 Initialize `bbsMessages` to an array of byte arrays containing the values in the
-`nonMandatory` array of strings encoded using the UTF-8 character encoding.
+`nonMandatory` array of strings encoded using the <a>UTF-8</a> <a>character encoding</a>.
             </li>
             <li>
 Compute the `bbsSignature` using the `Sign` procedure of [[CFRG-BBS-Signature]]