Shapes - fill to infinity/-infinity

Feature request - i want to be able to add a shape(rect) and be able to specify y value as follows:

1. first value based on y axis
2. second value fill to infinity/-inifnity

afaik today i can either set 'paper' and then both values are precentage based on graph area or 'y' and set both of them as points.

该 issue 没有指定文件、测试或入口点。首先定位 plotly.js 中的 shape 矩形处理以及其 paper 和 y 坐标逻辑；确定混合数值与 infinity 或 negative-infinity 的 y 边界应如何表示和渲染。完成的标准是：一个 shape 可以将一个 y 轴值与 infinity 或 negative-infinity 边界结合，并且该行为由适当的测试覆盖。