show method should be parseable

[cscherrer]

When possible, it's desirable for the displayed version of an object to parse to that same value. This package does not satisfy this:

julia> Normal(0,1)
Normal{Float64}(μ=0.0, σ=1.0)

julia> Normal{Float64}(μ=0.0, σ=1.0)
ERROR: MethodError: no method matching Normal{Float64}(; μ=0.0, σ=1.0)
Closest candidates are:
  Normal{Float64}(::Any, ::Any) where T at /home/chad/.julia/packages/Distributions/Iltex/src/univariate/continuous/normal.jl:35 got unsupported keyword arguments "μ", "σ"
Stacktrace:
 [1] top-level scope at REPL[18]:1

Could this be changed? Preferably, (μ=0.0, σ=1.0) would be a valid input (that would be pretty great) rather than removing them from the printed output

[matbesancon]

It's tricky because it needs introducing all the keyword arguments, which is done in #823