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

addons/csharp_ldtk_importer/Models/LdtkTileInstance.cs

@@ -0,0 +1,18 @@
+using System.Text.Json.Serialization;
+
+namespace CSharpLdtkImporter.Models;
+
+public class LdtkTileInstance
+{
+    // Pixel coordinates [x,y]
+    [JsonPropertyName("px")]
+    public int[] Px { get; set; }
+
+    // Tile ID in the tileset
+    [JsonPropertyName("t")]
+    public int TileId { get; set; }
+
+    // Flip bits (0=none, 1=X, 2=Y, 3=X&Y)
+    [JsonPropertyName("f")]
+    public int FlipBits { get; set; }
+}