submodule对gitea不管用，所以直接拉了一份拉格兰

Lagrange.Core/Lagrange.OneBot/Message/Entity/JsonSegment.cs

@@ -0,0 +1,29 @@
+using System.Text.Json.Serialization;
+using Lagrange.Core.Message;
+using Lagrange.Core.Message.Entity;
+
+namespace Lagrange.OneBot.Message.Entity;
+
+[Serializable]
+public partial class JsonSegment(string data)
+{
+    public JsonSegment(): this("") { }
+
+    [JsonPropertyName("data")] [CQProperty] public string Data { get; set; } = data;
+}
+
+[SegmentSubscriber(typeof(LightAppEntity), "json")]
+public partial class JsonSegment : SegmentBase
+{
+    public override void Build(MessageBuilder builder, SegmentBase segment)
+    {
+        if (segment is JsonSegment json) builder.LightApp(json.Data);
+    }
+
+    public override SegmentBase FromEntity(MessageChain chain, IMessageEntity entity)
+    {
+        if (entity is not LightAppEntity lightAppEntity) throw new ArgumentException("Invalid entity type.");
+        
+        return new JsonSegment(lightAppEntity.Payload);
+    }
+}