improvement: Add ot-change event emission to dropdown component on selection of item

[santanubiswas948]

The component effectively manages action lists and popover scenarios.

on selection of any item from dropdown action handler should trigger & keep it in a common place.

[knadh]

Since the dropdown component can contain arbitrary content, not just menu items, I think it's best if this is handled not at lib level, but in the implementations themselves, @click when using a lib like Alpine or simply an onclick or other means.