Marine benchmark dataset

[timcdlucas]

I think we're actually pretty short on marine covariates.

But anyway, some people are pushing this as a marine benchmark dataset. https://github.com/lifewatch/marinespeed

Judging by the url that data comes from this package is by @samualbosch. And that data are already being used within zoon here. https://github.com/lifewatch/sdmpredictors

So I guess it's not unreasonable to hope a module for these data will turn up anyway. Otherwise, it'd be good for one of us to do it one day...