Fixes bottom attached message bottom margin.

src/collections/message.less

@@ -223,6 +223,9 @@
   -moz-border-radius: 0em 0em 0.325em 0.325em;
   border-radius: 0em 0em 0.325em 0.325em;
 }
+.ui.bottom.attached.message:not(:last-child) {
+  margin-bottom: 1em;
+}
 .ui.attached.icon.message {
   display: block;
   width: auto;