Refactor/dropdown menu (#279)

* Created dropdown menu UI component with story

* Added all components for composing Dropdown Menus

* Better component naming and reordered stories

* Solved comment thread from review

front/src/modules/ui/components/menu/DropdownMenuSeparator.tsx

@@ -0,0 +1,8 @@
+import styled from '@emotion/styled';
+
+export const DropdownMenuSeparator = styled.div`
+  width: 100%;
+  height: 1px;
+
+  background-color: ${(props) => props.theme.mediumBorder};
+`;