Back to the "Future" theme (SB Messenger notifications)

[mdmintz]

The JavaScript library used for SB Messenger notifications used to use the "Future" theme by default. Then the default theme was changed to "Flat". We'll go back to the "Future" theme, as it may have better contrast on more sites... with a few adjustments to make it look even better, like this: (Outer glow caused by a box-shadow effect.)

Here's a GIF of --demo mode during an XKCD site test from earlier days:

It's a good GIF. Although XKCD no longer has their Store page, the GIF could make a nice addition to the main README file.