Remove formal dependency on dreamRs/colorscale?

[joethorley]

No description provided.

[evanamiesgalonski]

yup ill see if feasible

[evanamiesgalonski]

dreamRs/colorscale uses R6 methods so its pretty hard to see the internals and reproduce something similar. The reason we import that package is cos it does an amazing job of interpolating colour by adjusting both the hue and brightness together so the resulting gradients make it way easier to distinguish differences in plots.

I'd be keen to look around for some other approaches/dive further into their code but only if you are ok with me spending a fair bit of internal time on it.