How notch traversal works on MacBooks

Tailscale now has a full windowed UI. Before that, our app had to learn how to tell you it was hidden by The Notch.

Every time I get a new Mac, I run these commands to reduce the spacing between menu bar icons. Lets you fit at least 2x the number of items in the menu bar.

```

defaults -currentHost write -globalDomain NSStatusItemSpacing -int 2

defaults -currentHost write -globalDomain NSStatusItemSelectionPadding -int 2

```