Add usage details for Base.eachsplit

[logankilpatrick]

I am reading through the docs for [Base.eachsplit](https://docs.julialang.org/en/v1/base/strings/#Base.eachsplit) and right now its use case is not clear to me. I see that the type it returns is different than split, but the current example does not make it clear why I would want to use it instead of just split:

julia> split(a, ".")
2-element Vector{SubString{String}}:
 "Ma"
 "rch"

julia> collect(eachsplit(a, "."))
2-element Vector{SubString}:
 "Ma"
 "rch"

[jakobjpeters]

It looks like split primarily calls collect on eachsplit.

julia/base/strings/util.jl

Lines 592 to 596 in afb6c60

	function split(str::T, splitter;
	limit::Integer=0, keepempty::Bool=true) where {T<:AbstractString}
	itr = eachsplit(str, splitter; limit, keepempty)
	collect(T <: SubString ? T : SubString{T}, itr)
	end

The example for eachsplit could be made to match that for eachmatch.

julia> a = "Ma.rch"
"Ma.rch"

julia> b = eachsplit(a, ".")
Base.SplitIterator{String, String}("Ma.rch", ".", 0, true)

julia> collect(b)
2-element Vector{SubString}:
 "Ma"
 "rch"