自定义节点如何让主节点下通过addShape添加的图形支持create-edge

### 问题描述

树节点下通过addShape绘制节点的其他功能节点，我想让功能节点可以与其他节点建立关联

### 重现链接

无

### 重现步骤

无

### 预期行为

无

### 平台

- 操作系统: [macOS, Windows, Linux, React Native ...]
- 网页浏览器: [Google Chrome, Safari, Firefox]
- G6 版本: [4.5.1 ... ]

### 屏幕截图或视频（可选）


### 补充说明（可选）

_No response_

The issue contains no reproduction, files, tests, or entry points, and only asks whether shapes added under a custom tree node can participate in create-edge. Start by obtaining a minimal reproduction and tracing the custom-node and edge-creation documentation or entry points; done criteria should specify how the added shape connects to another node.

Written by the indexing model from the issue text.