Introduction of a Dropdown element in the Abstract Design System

The Abstract Design System now contains a Dropdown element. A Dropdown displays a button that toggles another UI element (e.g., a Menu).

Example:

<x-dropdown>
  <template #activator>Toggle Button</template>
  <x-menu>
    <x-menu-label>menu label</x-menu-label>
    <x-menu-item>menu content</x-menu-item>
  </x-menu>
</x-dropdown>