fix: support utf-16 encoding

lib/pkpass/pass_file.dart

@@ -36,7 +36,10 @@ class PassFile {
           final file = archive.files
               .singleWhere((element) => element.name == manifestEntry.key);
 
-          final content = file.byteContent;
+          final content = file.readBytes();
+          if (content == null) {
+            return;
+          }
 
           String hash = sha1.convert(content).toString();
 
@@ -80,7 +83,7 @@ class PassFile {
     );
     if (path == null) return null;
     final file = _folder.singleWhere((element) => element.name == path);
-    final content = file.byteContent;
+    final content = file.readBytes();
     return content;
   }
 
@@ -119,29 +122,25 @@ class PassFile {
 extension on ArchiveFile {
   String get stringContent {
     final codec = Charset.detect(
-          byteContent,
+          readBytes()!,
           defaultEncoding: utf8,
           orders: [
             utf8,
             ascii,
             gbk,
             latin1,
+            utf16,
           ],
         ) ??
         utf8;
-    return codec.decode(content);
-  }
-
-  Uint8List get byteContent {
-    decompress();
-
-    final content = this.content;
-    if (content is String) {
-      return utf8.encode(content);
-    } else if (content is Iterable) {
-      return Uint8List.fromList(content.cast<int>().toList());
-    } else {
-      return rawContent!.toUint8List();
+    try {
+      return codec.decode(content);
+    } on FormatException {
+      // utf8 and utf16 are hard to distinguish
+      if (codec is Utf8Codec) {
+        return utf16.decode(content);
+      }
+      rethrow;
     }
   }
 }