Vector fields docs

[smartalecH]

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Would be good to add a simple page in the docs that describe how fmmax computes vector fields. The paper describes this to some detail, but even since then, fmmax has changed it's approach.

Some interesting details include...

• FOMs used
• Comparisons of methods (especially compared to their FOURIER counterparts)
• When to use some vs others

We can start will a "brain dump" (it doesn't have to sound like a paper). But documenting this will help us keep things consistent.

[smartalecH]

Here's some good info:

https://github.com/facebookresearch/fmmax/blob/c6cd855fceb26fda5234ec704d1ea0cd0cbff6c9/src/fmmax/vector.py#L113-L130