add dependencies code

docs/dropdown.md

@@ -6,6 +6,11 @@
 It requires the [bootstrap-select](https://developer.snapappointments.com/bootstrap-select/)
 library and its dependencies.
 
+```html
+  <link rel="stylesheet" href="ui/bootstrap-select/dist/css/bootstrap-select.min.css">
+  <script src="ui/bootstrap-select/dist/js/bootstrap-select.min.js"></script>
+```
+
 Example:
 
 ```html