优化更新代码，添加界面功能并整合

ShrlAlgo.RvKits/RvFamily/FamilyLibrary/LoadedFamilyDropHandler.cs

@@ -0,0 +1,17 @@
+using Autodesk.Revit.DB;
+using Autodesk.Revit.UI;
+
+namespace ShrlAlgo.RvKits.RvFamily.FamilyLibrary
+{
+    public class LoadedFamilyDropHandler : IDropHandler
+    {
+        public void Execute(UIDocument document, object data)
+        {
+            ElementId familySymbolId = (ElementId)data;
+            if (document.Document.GetElement(familySymbolId) is FamilySymbol symbol)
+            {
+                document.PromptForFamilyInstancePlacement(symbol);
+            }
+        }
+    }
+}