feature: add support for multiple heatmaps

[thunderer199]

Change implementation from one layer to multiple layers. With the compatibility of one layer configuration from previous versions.

[itsmichaeldiego]

Hey, this is nice, thanks! Could you provide an example so we can test it out easily?

[thunderer199]

You can pass multiple configs to the heatmap prop. In other terms in stay unchanged. Not sure where is the best place to add example.
Maybe I can add some example right in the repo, to show how it works?

[itsmichaeldiego]

That would be amazing @thunderer199, thank you!