add pointerenter event to Menubar.CheckboxItem

[Juliiiian]

Problem:

On Menubar.CheckboxItem there are the events pointermove and pointerleave to detect hovering over the element. But when using the pointermove event it is fired on every move, which can be sometimes performance heavy and unnecessary, since it would just work with the pointerenter event.

Solution:

I don't know if it should be added to every component. For example, you can hover over an item in the menu to just show what it will change and then actually change it when clicked, like a preview (that's my use case).

[huntabyte]

If we add this to one of the menu item components we should add it to all of them. The only thing we'll need to do is forward the events from the elements and update the types to include the proper event for each of them.

[huntabyte]

Closed by #403