WIP: Adds FeatureCollection support

[iBotPeaches]

So was digging for a cool package to help with some GeoJSON parsing in our Laravel app, found this and it error`d out on initial parsing with:

Invalid GeoJSON: The type FeatureCollection is not supported

Seeing how it was open source, I dove in to fix/add and I noticed maybe why it was left unresolved. Thankfully after the last few days of spending time with GeoJSON, I got the spec down pretty well.

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Since Features are just a mixture of geometry and properties I figured this would be easy. Just supporting the existing parsing of geometry and a new parsing of custom key/value pairs.

Until I read the RFC. It says

A Feature object has a member with the name "properties". The value of the properties member is an object (any JSON object or a JSON null value).

So my idea of a simple key/value falls apart if you are allowed to have a JSON object (of any shape) or null.

However, as I started writing this. It was taking a good deal of changes to support introducing a new class that simply sub-classed Geometries and I felt a bit uneasy with how much I was changing.

Before I go further, may someone peek if I am going about this a wrong way or have any tips?

• I don't really like that I had to make a new factory class, but it felt wrong packing features onto Geometry classes as they live higher than that.

[iBotPeaches]

Just did the iterations/loops above this class. Closing.

[saibotk]

Hey 👋

First of all, thank you for raising a PR and doing a deep dive into the specifications 🫡

@ahawlitschek and me also want to address FeatureCollection at some point. We might try to do so rather sooner than later after seeing people having a use case for it.

Certainly if you still want to open a PR and provide some examples we are open to help you and work on a solution together 👌

Thanks for your work we appreciate it.