emit @mouseenter / @mouseleave events for vs__dropdown-menu

[wuschi]

We are using vue-select in a project with custom scrollable content.
When the dropdown menu is scrolled the parent page also gets scrolled.

It would be great if @mouseenter and @Mouseleave events could be emitted for the dropdown menu, so that scrolling of the parent page can be locked when those events are received.

As a workaround, i currently implemented the child option slots for being able to react to @mouseenter and @Mouseleave for each single option.