Serialize byteOffset as size_t, avoiding cast

Fixes silently writing an overflowed int in the output file.

tiny_gltf.h

@@ -7124,7 +7124,7 @@ static void SerializeGltfAccessor(const Accessor &accessor, detail::json &o) {
     SerializeNumberProperty<int>("bufferView", accessor.bufferView, o);
 
   if (accessor.byteOffset != 0)
-    SerializeNumberProperty<int>("byteOffset", int(accessor.byteOffset), o);
+    SerializeNumberProperty<size_t>("byteOffset", accessor.byteOffset, o);
 
   SerializeNumberProperty<int>("componentType", accessor.componentType, o);
   SerializeNumberProperty<size_t>("count", accessor.count, o);