[ticket/15949] Add ucp_profile_signature_posting_editor_options_prepend

It adds a template event in the signature posting editor to add custom
options to be consistent with the default posting editor.

PHPBB3-15949

phpBB/styles/prosilver/template/ucp_profile_signature.html

@@ -24,6 +24,7 @@
 	<!-- INCLUDE posting_editor.html -->
 	<h3>{L_OPTIONS}</h3>
 	<fieldset>
+		{% EVENT ucp_profile_signature_posting_editor_options_prepend %}
 		<!-- IF S_BBCODE_ALLOWED -->
 			<div><label for="disable_bbcode"><input type="checkbox" name="disable_bbcode" id="disable_bbcode"{S_BBCODE_CHECKED} /> {L_DISABLE_BBCODE}</label></div>
 		<!-- ENDIF -->