Currently we only have a dark theme icon with white and grey dots over
a black background. For some desktops, a logo with black and grey dots
over a white background might be preferable. And for desktops where the
bar is *almost* black or white, but not quite, an option to render the
logo with dots only and no background can look really nice.
Add a new -theme flag to the systray command with the default staying
the same as it is today.
Updates #18303
Change-Id: Ia101a4a3005adb9118051b3416f5a64a4a45987d
Signed-off-by: Will Norris <will@tailscale.com>
2d85f37f39