Add a Super Nintendo theme

[christopherkenny]

Lots of greys and purples:

[lcpilling]

I love it but could you use the colours from the buttons for some of the discrete scale values or something? Otherwise it is quite uniform

[christopherkenny]

Those are there, they're just not used in the shorter discrete example. I've reordered them to avoid the double-purple.

code for plot

``` palette::palette(snes_palette) |> plot() ```

I think this makes the plot a little more vibrant:

What do you think?

[lcpilling]

Nice, looks much better to me

[MatthewBJane]

Awesome!!!