ptyxis: add target

[0xda157]

I assert that this feature request is relevant for Stylix

• [x] I assert that this is not a duplicate of an existing feature request.

Description

libadwaita terminal, to be used as default terminal in ubuntu 25.10

example theme: https://gitlab.gnome.org/chergert/ptyxis/-/blob/main/data/palettes/spacedust.palette?ref_type=heads

[0xda157]

I'll work on getting a basic home-manager module setup for ptyxis