feat: switch to pure-rust jxl decoder

this makes the logic drastically simpler;
as it comes with image crate integration.

however, images can no longer be saved as JXL with this version
(as jxl-oxide is decoder-only)

Cargo.toml

@@ -8,8 +8,12 @@ license = "AGPL-3.0-or-later"
 iced = { version = "0.14.0", features = [ "image" ] }
 dirs = "6.0.0"
 rfd = "0.17.2"
-jpegxl-rs = "0.14.0"
 
 [dependencies.image]
 version = "0.25.10"
 features = [ "avif-native" ]
+
+[dependencies.jxl-oxide]
+version = "0.12.6"
+# I really wish the image crate was named better
+features = [ "image" ]