snappy-switcher: add target

[Neubulae]

Description

This is listed as one of the recommended switcher on Hyprland. They have some interesting style configuration, but it's not controlled thru nix files and I have to link them thru home-manager, so maybe an integrated support from Stylix is an appropriate choice.

Submission Checklist

• I assert that this issue is relevant to Stylix
• I assert that this is not a duplicate of an existing issue