add initial implementation of LDtk importer with data models and scene builder

addons/csharp_ldtk_importer/Models/LdtkLevel.cs

@@ -0,0 +1,12 @@
+using System.Text.Json.Serialization;
+
+namespace CSharpLdtkImporter.Models;
+
+public class LdtkLevel
+{
+    [JsonPropertyName("identifier")]
+    public string Identifier { get; set; }
+
+    [JsonPropertyName("layerInstances")]
+    public LdtkLayerInstance[] LayerInstances { get; set; }
+}