add GeoJSON Layer Display

I propose for Plotly the ability to overlay multiple GeoJSON objects on a map, each with a distinct color and corresponding legend, without the need to bind them to a specific data attribute (like z in choropleth maps).

Currently, Plotly.js requires GeoJSON features to be associated with data for visualization. However, there are use cases, including one of my own, where the goal is simply to display the shapes defined by GeoJSON files, differentiate them with colors, and provide a legend for reference. This is purely for visual comparison and spatial representation.

For example, I have two GeoJSON datasets representing which type of agricultural simulation performed better for a region: Yield Potential (in blue) and Rainfed Potential (in yellow). I want to display these on a map, each with a random but consistent color, and include a legend to identify them. See this example image for reference.

Implementing this feature would benefit users who need to visualize spatial data layers without additional data-driven coloring. It would enhance Plotly's functionality and maintain consistency within applications that rely on Plotly for other types of data visualization.

I am open to trying contributing to the development of this feature and would like to hear the community's and maintainers' thoughts on its potential inclusion in Plotly.js.

首先检查 Plotly.js 对地图和等值区域图的支持，尤其是当前如何将 GeoJSON 要素与数据关联。确定在没有 z 属性的情况下显示多个具有不同颜色和图例条目的 GeoJSON 图层的范围。该 issue 未提供文件或测试位置，因此需要确定相关的入口点和验收测试。