Port PSN pkg decryption to pure Python (drop Wine requirement)

data/bin/ATTRIBUTION.md

@@ -1,7 +1,9 @@
 # pkg2zip
 
-The `pkg2zip.exe` binary in this folder decrypts and extracts NoPayStation
-`.pkg` files (PSP / PSX / PS3 / PSVita content).
+The `pkg2zip.exe` binary in this folder is kept as an optional fallback for
+decrypting NoPayStation `.pkg` files (PSP / PSX / PS3 / PSVita content). The
+app normally uses its own pure-Python decryptor (`app/pkg.py`) and only runs
+this binary if that fails.
 
 - Project: <https://github.com/mmozeiko/pkg2zip>
 - Author: Marcin Mikołajczak (mmozeiko)