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

addons/csharp_ldtk_importer/Models/LdtkData.cs

@@ -0,0 +1,30 @@
+using System.Text.Json.Serialization;
+
+namespace CSharpLdtkImporter.Models;
+
+public class LdtkData
+{
+    [JsonPropertyName("levels")]
+    public LdtkLevel[] Levels { get; set; }
+
+    [JsonPropertyName("defs")]
+    public LdtkDefinitions Defs { get; set; }
+}
+
+public class LdtkDefinitions
+{
+    [JsonPropertyName("tilesets")]
+    public LdtkTilesetDef[] Tilesets { get; set; }
+}
+
+public class LdtkTilesetDef
+{
+    [JsonPropertyName("uid")]
+    public int Uid { get; set; }
+
+    [JsonPropertyName("relPath")]
+    public string RelPath { get; set; }
+    
+    [JsonPropertyName("tileGridSize")]
+    public int TileGridSize { get; set; }
+}