Add doctest: eachslice (#36386)

* add doctests for eachslice

* update doctest eachslice

Author: mgautam98

base/abstractarraymath.jl

@@ -514,6 +514,28 @@ See also [`eachrow`](@ref), [`eachcol`](@ref), and [`selectdim`](@ref).
 
 !!! compat "Julia 1.1"
      This function requires at least Julia 1.1.
+
+# Example
+
+```jldoctest
+julia> M = [1 2 3; 4 5 6; 7 8 9]
+3×3 Array{Int64,2}:
+ 1  2  3
+ 4  5  6
+ 7  8  9
+
+julia> first(eachslice(M, dims=1))
+3-element view(::Array{Int64,2}, 1, :) with eltype Int64:
+ 1
+ 2
+ 3
+
+julia> collect(eachslice(M, dims=2))
+3-element Array{SubArray{Int64,1,Array{Int64,2},Tuple{Base.Slice{Base.OneTo{Int64}},Int64},true},1}:
+ [1, 4, 7]
+ [2, 5, 8]
+ [3, 6, 9]
+```
 """
 @inline function eachslice(A::AbstractArray; dims)
     length(dims) == 1 || throw(ArgumentError("only single dimensions are supported"))