MacOS: make Monu center / align under toolbar icon

[bnvk]

Currently, the toolbar UI is horizontally aligning itself a ways away from where the Monu icon is. This is a tad bit jarring UI wise... see pic:

I'm not sure if Atom-Shell allows for centering it near the toolbar icon, or somehow that is impossible to figure out given current API.

I'll try to research this a little bit

[sindresorhus]

See electron/electron#1500

[marcbachmann]

That was implemented in max-mapper/menubar@974ba00