Improve headline

wiki/src/doc/about/openpgp_keys/signing_key_revocation.mdwn

@@ -291,7 +291,8 @@ XXX: - Include "You can read a complete description of the distribution mechanis
 XXX: - Stop before "So, can we count on you for this?"
 </pre>
 
-### To add new members
+Adding a new member
+-------------------
 
 1. Send the [[invitation email|signing_key_revocation#invitation]] to
    the new member.