call AutoDispose(), dispose VRMImporterContext OnDestroy

VRMAutoDisposer.cs

using UnityEngine;

namespace VRM.Extension
{
    public class VRMAutoDisposer : MonoBehaviour
    {
        public VRMImporterContext Context;

        private void OnDestroy()
        {
            Context?.Dispose();
        }
    }

    public static class VRMAutoDisposerExtension
    {
        public static void AutoDispose(this VRMImporterContext context)
        {
            var disposer = context.Root.AddComponent<VRMAutoDisposer>();
            disposer.Context = context;
        }
    }
}