Document pathOptions for GeoJSON

[bb]

This adds documentation for the GeoJSON showing that it has pathOptions prop, same as Rectangle et al.

It's marked Mutable like for the other Components and changing it is actually delegated to the leaflet object, however it does not work as it needs resetStyle() to be called.

Setting a different color or weight via pathOptions on a <Rectangle.../> did neither work for me, so I wonder if it's a bug or if is intended but the documentation is misleading.

Edit: Nevermind the update issues. It's updating. I was setting only the sub-property not the whole pathOptions. My problem can be reproduced with the third case within in https://codesandbox.io/s/xenodochial-proskuriakova-pytgj?file=/src/Map.js:8695-8722 and is most likely intentional functionality.

[PaulLeCam]

Thanks for the PR!
Yes props are compared by reference so if you want to mutate fields in an object, you need to provide a new object.