Port geosimplify-js

Nobody has claimed this yet.

[`LineString.simplify(tolerance:highestQuality:)`](https://mapbox.github.io/turf-swift/2.3.0/Structs/LineString.html#/s:4Turf10LineStringV8simplify9tolerance14highestQualityySd_SbtF) and [`simplified(tolerance:highQuality:)`](https://mapbox.github.io/turf-swift/2.3.0/Structs/LineString.html#/s:4Turf10LineStringV10simplified9tolerance14highestQualityACSd_SbtF) are based on [simplify-js](https://github.com/mourner/simplify-js/), which is fine for certain simplification use cases. However, sampling the input to a map matching algorithm requires interpolating points along a straightaway: https://github.com/mapbox/mapbox-directions-swift/issues/661#issuecomment-1063184448. The standard Ramer–Douglas–Peucker algorithm can easily create a space between vertices large enough to result in a gap according to the map matching algorithm.

[geosimplify-js](https://github.com/mapbox/geosimplify-js/) is a derivative of simplify-js that preserves points along straightaways. It could be ported to Swift as an alternative to the usual simplification algorithm. Suggested method signatures:

```swift
mutating func simplify(minimumOffset: LocationDistance, minimumGap: LocationDistance)
func simplified(minimumOffset: LocationDistance, minimumGap: LocationDistance)
```

/cc @danpat @Guardiola31337

Start by reading the existing LineString.simplify and simplified methods, then compare their behavior with the linked geosimplify-js project and the map-matching context. Done means adding the suggested Swift methods with minimumOffset and minimumGap that preserve points along straightaways.

Written by the indexing model from the issue text.