add reply icon on mobile

templates/partials/topic/reply-button.tpl

@@ -1,5 +1,5 @@
-<div component="topic/reply/container" class="btn-group action-bar <!-- IF !privileges.topics:reply -->hidden<!-- ENDIF !privileges.topics:reply -->">
-	<a href="{config.relative_path}/compose?tid={tid}&title={title}" class="btn btn-primary" component="topic/reply" data-ajaxify="false" role="button">[[topic:reply]]</a>
+<div component="topic/reply/container" class="btn-group action-bar bottom-sheet <!-- IF !privileges.topics:reply -->hidden<!-- ENDIF !privileges.topics:reply -->">
+	<a href="{config.relative_path}/compose?tid={tid}&title={title}" class="btn btn-primary" component="topic/reply" data-ajaxify="false" role="button"><i class="fa fa-reply visible-xs-inline"></i><span class="visible-sm-inline visible-md-inline visible-lg-inline"> [[topic:reply]]</span></a>
 	<button type="button" class="btn btn-info dropdown-toggle" data-toggle="dropdown">
 		<span class="caret"></span>
 	</button>