add dir to docstrings and tests

Author: jClugstor

src/dense.jl

@@ -115,6 +115,7 @@ Defined by [ADTypes.jl](https://github.com/SciML/ADTypes.jl).
   - `fdhtype::T3`: finite difference type for the Hessian
   - `relstep`: relative finite difference step size
   - `absstep`: absolute finite difference step size
+  - `dir`: direction of the finite difference step
 """
 Base.@kwdef struct AutoFiniteDiff{T1, T2, T3, S1, S2, S3} <: AbstractADType
     fdtype::T1 = Val(:forward)

test/dense.jl

@@ -69,8 +69,9 @@ end
     @test ad.fdhtype === Val(:hcentral)
     @test ad.relstep === nothing
     @test ad.absstep === nothing
+    @test ad.dir
 
-    ad = AutoFiniteDiff(; fdtype = Val(:central), fdjtype = Val(:forward), relstep = 1e-3, absstep = 1e-4)
+    ad = AutoFiniteDiff(; fdtype = Val(:central), fdjtype = Val(:forward), relstep = 1e-3, absstep = 1e-4, dir = false)
     @test ad isa AbstractADType
     @test ad isa AutoFiniteDiff
     @test mode(ad) isa ForwardMode
@@ -79,6 +80,7 @@ end
     @test ad.fdhtype === Val(:hcentral)
     @test ad.relstep == 1e-3
     @test ad.absstep == 1e-4
+    @test !ad.dir
 end
 
 @testset "AutoFiniteDifferences" begin