update solver docs strings

src/NeuralDELux.jl

@@ -1,12 +1,14 @@
 module NeuralDELux
 
+using DocStringExtensions
+
 include("gpu.jl")
 include("neuralde.jl")
 include("solver.jl")
 include("training.jl")
 include("utils.jl")
 include("loss.jl")
 
-export ADNeuralDE, SciMLNeuralDE, ADEulerStep, ADRK4Step
+export ADNeuralDE, SciMLNeuralDE, ADEulerStep, ADRK4Step, MultiStepRK4
 
 end

src/solver.jl

@@ -118,6 +118,11 @@ function solve(prob::AbstractDEProblem, solver::SciMLRK4Step; kwargs...)
     @muladd cat(u, u + (dt/6) .* (k₁ + 2 .* (k₂ + k₃) + f(u + dt .* k₃, p, t + dt)), dims=ndims(u)+1)
 end 
 
+"""
+($TYPEDSIGNATURES)
+
+Zygote and GPU compatible fixed step size RK4 solver. Needs to be called similar to the solvers of `OrdinaryDiffEq.jl`. `dt` is a mandatory kwarg, setting the step size.
+"""
 struct MultiStepRK4
 end