feat: 1.固定图层缩略图（完成）

2.工具栏新增插槽（完成）
3.loadJSON的元素顺序回发生错误

src/component/Canvas/CanvasEditor/commands/RedGreenCommands.js

@@ -358,7 +358,7 @@ export class BatchInitializeRedGreenModeCommand extends Command {
 
       this.canvas.add(object);
       this.canvas.sendToBack(object);
-      backgroundLayer.fabricObject = object;
+      backgroundLayer.fabricObject = object.toObject(["id", "layerId", "type"]);
     } else {
       // 更新现有背景对象大小
       object.set({