Add Support for Changing the Tray Icon

The proposed change adds support for changing the tray icon in the Linux version.

The current icon used for the tray is the same as the application’s icon which has a blue background, this does not match other tray icons on most common Linux desktop themes which are monochromatic.

Electron does not provide an easy way to specify an icon that can be adapted to the current theme in Linux, so this allows the user to pick an icon that matches their desktop theme.

Getting the icon to look half-way decent is still a problem due to the lack of SVG support in Electron.

In the settings window there will be a new drop-down labeled ‘Tray Icon’ with default, light and dark options.

There are a few other posts relating to the tray icon appearance:

Pull requests:

Thanks @gareth! I moved this to the GitHub contributions section so we can engage our engineering and UI/UX folks :+1: