Add anchor to template email

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

@@ -305,6 +305,10 @@ Adding a new member
 
 1. Ask the new member to confirm the reception of their share.
 
+<a id="sharing"></a>
+
+### Sharing email
+
 <pre>
 Subject: sharing