Add org.matrix.cross_signing_reset navigation action

Signed-off-by: Johannes Marbach <n0-0ne+github@mailbox.org>

Author: Johennes

proposals/4312-x-signing-reset-with-nextgen-auth.md

@@ -52,6 +52,11 @@ client can complete the stage without further parameters.
 }
 ```
 
+To facilitate the navigation, a new action `org.matrix.cross_signing_reset` is introduced and MAY be
+used in the `account_management_actions_supported` authorization server metadata field from
+[MSC4191]. Servers SHOULD use this action to deep link the user if the authorization server supports
+it.
+
 ## Potential issues
 
 Semantically, resetting cross-signing keys doesn't fall into the authorization server's domain. The