feat: add a badge in the menu bar icon to show switch connection state

[ericfitz]

We need to decorate the menu bar icon with a badge that shows whether or not a foot switch is connected

red/green light would be nice, but is not color blind friendly

• could use presence/absence of an icon
• could use connected/disconnected icons
• could use red/green ball (would be nice to have small, diffuse rather than big circle) - but would have to support color blind palette too
  • so maybe a switch in the settings for "use color blind palette" that would use blue/orange colors (okabe-ito) rather than red/green

The icon should update automatically, just like the settings UI updates automatically