feat: add Enter, Mouse and Leave events

[amrbashir]

closes #123

[amrbashir]

@pewsheen as always, can you take care of macOS part? thanks

[pewsheen]

@pewsheen as always, can you take care of macOS part? thanks

The left and right mouse up event is quite unreliable on macOS. It will be ignored when the menu poped up.

[amrbashir]

thanks @pewsheen, LGTM

[nongyehong]

Ah, so how can I determine the position of my system icon, I think this hover mouse event can expand a lot of functions

[amrbashir]

you can call icon.rect() to get the position and size of the icon at any given time, also all the events include the position of the cursor when that event was triggered.

[yume-chan]

I wonder why double left click support was removed?