feat(dropdown): vertical dropdown menu item

Allows dropdown menu item's text and description to stack vertically

Closes #1059

Author: rkomiyama

src/definitions/modules/dropdown.less

@@ -137,6 +137,11 @@
   border-top-width: 0;
 }
 
+.ui.dropdown .menu > .item.vertical {
+  display: flex;
+  flex-direction: column-reverse;
+}
+
 /*--------------
   Floated Content
 ---------------*/
@@ -215,6 +220,18 @@
   color: @itemDescriptionColor;
 }
 
+.ui.dropdown .menu > .item.vertical > .description {
+  margin: 0;
+}
+
+/*-----------------
+      Item Text
+-------------------*/
+
+.ui.dropdown .menu > .item.vertical > .text {
+  margin-bottom: @verticalItemMargin;
+}
+
 /*-----------------
        Message
 -------------------*/

src/themes/default/modules/dropdown.variables

@@ -63,6 +63,9 @@
 @itemBoxShadow: none;
 @itemMinHeight: unit(@itemLineHeight + 2 * @itemVerticalPadding, rem);
 
+/* Vertical Item */
+@verticalItemMargin: 0.25em;
+
 /* Sub Menu */
 @subMenuTop: 0;
 @subMenuLeft: 100%;