Allow custom color scales across sisl.viz

[pfebrer]

Closes #785

Now one can pass a custom colorscale to any colorscale argument in the plots of sisl.viz.

E.g.:

import sisl

plot = sisl.geom.graphene().tile(2, 0).plot(
    atoms_style={"color": [0, 0.25, 0.75, 1]}, 
    atoms_colorscale=["rgb(255, 0, 0)", "rgb(0, 0, 255)"], 
)

plot

plot.update_inputs(axes="xy", atoms_scale=20, backend="matplotlib")

All plotly named colorscales (e.g. "balance") also work now for the 3D geometry plot.

Thanks @saru1799!

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 51.72414% with 14 lines in your changes missing coverage. Please review.

Project coverage is 87.28%. Comparing base (255efb1) to head (e83dba0). Report is 1 commits behind head on main.

Files	Patch %	Lines
src/sisl/viz/figure/matplotlib.py	38.46%	8 Missing :warning:
src/sisl/viz/plotutils.py	33.33%	4 Missing :warning:
src/sisl/viz/figure/plotly.py	50.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #786 +/- ## ========================================== - Coverage 87.28% 87.28% -0.01% ========================================== Files 397 397 Lines 50919 50925 +6 ========================================== + Hits 44446 44448 +2 - Misses 6473 6477 +4 ```

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