Add monochrome launcher icon for android 13

First up, big thanks for your work on stealth, big fan~

I noticed stealth does not support monochrome/themeable icons yet, which makes it stick out quite a bit when placed next to apps that do support it on the home screen - so I added a simple monochrome icon, keeping it as close as possible to the original color version.

Here's a side by side showing the themed and un-themed version next to some other themed apps:

Also, here's the raw SVG I used for the monochrome icon, in case you want to tweak something: (it is white on white here and very small but its there haha)

Cheers!