fix(Dropdown): handle keyboard events for arrows, space and enter keys locally (#4004)

* fix(Dropdown): handle keyboard events for arrows, space and enter keys locally

* remove only and usused returns

* fix `selectedIndex` on search

Author: layershifter

docs/src/examples/modules/Dropdown/States/DropdownExampleDisabledItem.js

@@ -8,7 +8,7 @@ const options = [
 ]
 
 const DropdownExampleDisabledItem = () => (
-  <Dropdown text='Dropdown' options={options} open />
+  <Dropdown text='Dropdown' options={options} />
 )
 
 export default DropdownExampleDisabledItem