Improve Documentation for HaversineIntermediate

[JosiahParry]

Documentation for HaversineIntermediate trait can be improved.

Notably the parts that can be improved are the function arguments f for haversine_intermediate() and max_dist and include_ends for haversine_intermediate_fill().

• I think the f is short for fraction of the distance between self and other.
• I think haversine_intermediate_fill() returns a vector of the points that are interpolated between self and other

If some clarity can be provided in this issue I'd be happy to make a PR

https://github.com/georust/geo/blob/d13e70c6438d4b8a845a1403afb8db4ec146f251/geo/src/algorithm/haversine_intermediate.rs#L6

[JayKickliter]

I was just about to open this same exact issue for GeodesicIntermediate.

[JayKickliter]

I'd be happy to open a PR if someone more familiar with domain can confirm @JosiahParry's deductions.

[michaelkirk]

I don't use either of those traits, but taking a quick look at the code, your interpretation seems correct to me @JosiahParry.

Looking at the git archeology, it seems probable that the docs/names for the GeodesicIntermediate were copy/pasted from HaversineIntermediate.

If either of you want to open PRs with better docs, that'd be excellent.