add: LoadingScene, ProxyNode

src/DataStructures/ProgressInfo.cs

@@ -0,0 +1,9 @@
+namespace Polonium.DataStructures;
+
+public abstract class ProgressInfo
+{
+    public int CurrentTaskIndex { get; set; }
+    public int TotalTasks { get; set; }
+    public abstract float Progress { get; }
+    public string Message { get; set; }
+}