Some of the documentation is only added in an @require block. This leads to warnings with newer Documenter versions when loading the corresponding optional packages. Example:

julia> using LazySets, Polyhedra
┌ Warning: Replacing docs for `LazySets.HPolytope :: Union{Tuple{Union{HRepresentation{N}, Polyhedron{N}}}, Tuple{N}} where N` in module `LazySets`
└ @ Base.Docs docs/Docs.j

Add edocs. In theory they could be identical to the OTP, but simple copying will (?) violate OTP's APL license

x = sample(1000)
y = sample(1000)

sx = Set$new(x)
sy = Set$new(y)

microbenchmark::microbenchmark(
  setdiff(x, y),
  sx - sy,
  unit = "s"
)

Gives a mean time in seconds of:

setdiff(x,y) = 4.681405e-05
sx - sy = 1.639163e-02

A considerable difference. The additional bloat is due to a lot of checks that sort through the correct dispatch methods and use tricks for

In index.md, when one package uses MathematicalSets, add a subsection like the following:

## Usage

The following packages implement the `MathematicalSets.AbstractSet` interface:

|Library|Description|
|-------|------------|
|[LazySets](https://github.com/JuliaReach/LazySets.jl)|A Julia package for calculus with convex sets|
|[Polyhedra](https://github.com/JuliaPolyhedra/Polyhed