`namedtuple` for empty `Dict`

[JinraeKim]

How about converting Dict() to NamedTuple()?

julia> dict = Dict(:a => 1)
Dict{Symbol, Int64} with 1 entry:
  :a => 1

julia> using NamedTupleTools

julia> NamedTupleTools.namedtuple(dict)
(a = 1,)

julia> NamedTupleTools.namedtuple(Dict())
ERROR: MethodError: no method matching namedtuple(::Dict{Any, Any})
Closest candidates are:
  namedtuple(::DataType) at /Users/jinrae/.julia/packages/NamedTupleTools/GZxRn/src/NamedTupleTools.jl:102
  namedtuple(::String...) at /Users/jinrae/.julia/packages/NamedTupleTools/GZxRn/src/NamedTupleTools.jl:199
  namedtuple(::Tuple{Vararg{Symbol, N}}) where N at /Users/jinrae/.julia/packages/NamedTupleTools/GZxRn/src/NamedTupleTools.jl:196
  ...
Stacktrace:
 [1] top-level scope
   @ REPL[4]:1

julia> (;)
NamedTuple()  # expected result

[JeffreySarnoff]

Thank you. I have implemented this for a future (soon) version.
I will add it into the current version.