🤔 [QUESTION]线图层的端点如何共享

### 🐛 Question description [Please make everyone to understand it]
当有多次绘制的情况 线段A 中的任意点 无法作为线段B的开始点
目前只能通过吸附功能 让线段A中的点作为 线段B的途中点
### 💻 Link to minimal reproduction

Please provide a link by forking these links [L7 Draw](https://codesandbox.io/s/l7draw-issue-template-df75t7) or GitHub repo. What is a minimal reproduction, and why is it required?

### 🏞 Expected result

### 🚑 Any additional [like screenshots]

- **L7Draw Version**:
- **Platform**:

Start by reproducing the endpoint-sharing behavior in the linked L7 Draw CodeSandbox template. Compare drawing a second line from an existing point with the current snapping behavior, and clarify the expected result before locating the relevant interaction entry point. Done means a point from line A can serve as the starting point of line B without relying on it as an intermediate snapped point.

Written by the indexing model from the issue text.