Fixed showlegend for plotly

[nastya236]

Fixed showlegend **kwargs in plotly scatter 3D.

from cebra.integrations.plotly import plot_embedding_interactive
import numpy as np

embedding = np.random.randn(100, 3)
labels = np.random.randint(0, 10, 100)

plot_embedding_interactive(embedding, labels, markersize=10, showlegend=True)

plot_embedding_interactive(embedding, labels, markersize=10)

[stes]

Is it possible to write a test for this? Or at least add an example to how this is used? Does it affect the older plots in any way, @nastya236 ?

[nastya236]

Of course, writing test for this. I made some modifications in the last commit.
Update: tests are added and passed, ready for the review @stes

[MMathisLab]

lgtm for discrete! I guess the idea is if the data is continuous the legend could be a bar with a color gradient?

[stes]

thanks!