Handle palette images with translucency (#7)

* Handle palette images with translucency

Images with transparency stored in the palette format were assumed opaque

* Reformat

Author: gentlegiantJGC

src/amulet/resource_pack/java/resource_pack_manager.py

@@ -151,6 +151,10 @@ def _load(self, progress_manager: AbstractProgressManager) -> None:
                             if im.mode == "RGBA":
                                 alpha = numpy.array(im.getchannel("A").getdata())
                                 texture_is_transparent = bool(numpy.any(alpha != 255))
+                            elif im.mode == "P":
+                                texture_is_transparent = (
+                                    im.info.get("transparency", 0) != 0
+                                )
                             else:
                                 texture_is_transparent = False