Allow to pass header items

app/assets/javascripts/gl_dropdown.js.coffee

@@ -222,8 +222,12 @@ class GitLabDropdown
   renderItem: (data) ->
     html = ""
+    # Separator
     return "<li class='divider'></li>" if data is "divider"
+    # Header
+    return "<li class='dropdown-header'>#{data.header}</li>" if data.header?
+
     if @options.renderRow
       # Call the render function
       html = @options.renderRow(data)