`size(dist)`?

[penelopeysm]

Plaice has some code that looks like this now:

Plaice.vec_length(d::PM.MvNormal) = length(d.μ)
function Plaice.optic_vec(d::PM.MvNormal)
    return [VarNames.@opticof(_[i]) for i in eachindex(d.μ)]
end

# ...

Plaice.vec_length(d::PM.Multinomial) = length(d.p)
function Plaice.optic_vec(d::PM.Multinomial)
    return [VarNames.@opticof(_[i]) for i in eachindex(d.p)]
end

It would be nice if PM defined Base.size(dist) so that I could remove these duplicates.