Implement tooltips for Swing about systemtray

[dorkbox]

Added via commit 65e7c66 and 64bd95d.

Of note: tooltips are supported by Swing and GtkStatusIcons. AWT and AppIndicator menus do not support tooltips -- as such, there is a 1-time warning emitted so developers are aware they are using a feature that is not consistent across all platforms.

[dorkbox]

I'll add support for tooltips, but not for 3.2 release (since that is almost ready to go out the door). I think it's OK to have tooltips in swing, because I fixed the Swing tray icon transparency issue for Linux - so Swing trays now behave nicely on all OSes.

EDIT: This is needed to prevent a code split for testing, so this will be included in 3.2

[dorkbox]

check out the pre-release here