Convex Hull node

This node should convert vector shapes into convex hulls of their shapes, preserving their convex curves and bridging their concave parts with straight lines.

~~@Keavon Just wanted a run-down of how you want this to work. I'll be implementing a standard algorithm but wanted to ask if you had any specific functionality in mind.~~

~~Edit:
Information for whoever wants to tackle this task:~~

~~While there is plenty of literature about building the convex hull from polygons (polylines), there is much less on the internet about algorithms for doing that from bezier curves. You'll have to do some additional research to solve this, either through Googling for online resources or reading academic papers or thinking through a solution to the problem yourself as an extension of one of the polyline algorithms. The same algorithm needs to work for both shapes such as a hexagon and a circle.~~

未指定文件、测试或入口点。首先定位 vector-shape 节点的实现，然后研究适用于多边形和 Bézier 曲线的凸包算法；当一个算法能够同时处理六边形等多边形形状和圆形等曲线形状，保留凸曲线，并用直线连接凹陷部分时，即可视为完成。

由索引模型根据 Issue 内容生成。