broadcast perm mul

[GiggleLiu]

julia> pm = PermMatrix([3, 2, 4, 1], [0.2, 0.6, 0.1, 0.3])
4×4 SDPermMatrix{Float64, Int64, Vector{Float64}, Vector{Int64}}:
 0.0  0.0  0.2  0.0
 0.0  0.6  0.0  0.0
 0.0  0.0  0.0  0.1
 0.3  0.0  0.0  0.0

julia> res = pm .* 3im
4×4 SDPermMatrix{ComplexF64, Int64, Vector{ComplexF64}, Vector{Int64}}:
 0.0+0.0im  0.0+0.0im  0.0+0.6im  0.0+0.0im
 0.0+0.0im  0.0+1.8im  0.0+0.0im  0.0+0.0im
 0.0+0.0im  0.0+0.0im  0.0+0.0im  0.0+0.3im
 0.0+0.9im  0.0+0.0im  0.0+0.0im  0.0+0.0im

[Roger-luo]

I think you don't need to specialize on *, defining a custom broadcast-style would make this more generic, but I think this is also fine...