editorial: add code tag

Co-authored-by: Emil Lundberg <emil@yubico.com>

index.bs

@@ -1806,7 +1806,7 @@ a numbered step. If outdented, it (today) is rendered either as a bullet in the
                 ::  whose value is an {{AuthenticationExtensionsClientOutputs}} object containing [=extension identifier=] →
                     [=client extension output=] entries. The entries are created by running each extension's
                     [=client extension processing=] algorithm to create the [=client extension outputs=], for each
-                    [=client extension=] in |options|.{{PublicKeyCredentialCreationOptions/extensions}}.
+                    [=client extension=] in <code>|options|.{{PublicKeyCredentialCreationOptions/extensions}}</code>.
 
 
             1.  Let |constructCredentialAlg| be an algorithm that takes a [=global object=]