Added tileModel rl api "getIsFlat"

runelite-api/src/main/java/net/runelite/api/SceneTileModel.java

@@ -117,4 +117,6 @@ public interface SceneTileModel
 	int getOverlayNwColor();
 
 	void setOverlayNwColor(int color);
+
+	boolean getIsFlat();
 }

runescape-api/src/main/java/net/runelite/rs/api/RSSceneTileModel.java

@@ -60,4 +60,7 @@ public interface RSSceneTileModel extends SceneTileModel
 	@Import("triangleTextureId")
 	@Override
 	int[] getTriangleTextureId();
+
+	@Import("isFlat")
+	boolean getIsFlat();
 }