Focus mis-direction on MacOS when navigating popup with tab key

[prushforth]

According to our eyes and #335, when using FireFox on MacOS, if you open a popup and hit Tab, instead of moving to the |< affordance (the first after the popup content), the focus hops to the browser reload button, making a very awkward experience.

Other annoyances:

• Can't pan map with keyboard controls (e.g. arrow keys?)
• Can't pan map with touchpad scroll (zooms instead. expectation: 2-finger scroll gesture should pan) this is the same behaviour on Google Maps fwiw

[Malvoz]

https://www.a11yproject.com/posts/macos-browser-keyboard-navigation/:

By default, Apple computers have an operating system (OS) level setting that limits the Tab key to "Text boxes and lists only". This can be confusing, if not frustrating, for those unaware of this setting and expect keyboard focus to be similar to navigating on a Windows machine.

In the macOS settings, the "All Controls" setting must be enabled for all focusable interactive elements (for instance, links) to be keyboard accessible via the Tab key alone.