Docs: Adds metrics guide

[dvsrepo]

No description provided.

[dvsrepo]

Hi @dcfidalgo and @frascuchon. It would be great to be to visualize Plotly plots in the docs. However, there seems to be a long pending issue with the interplay between rtd theme/sphinx and the plotly.js bundle. You can see the console error here:

https://rubrix.readthedocs.io/en/docs-metrics_guide/guides/metrics.html

The main resources that I found for trying to solve this issue are (I've tried two things with no luck, see commits):

readthedocs/sphinx_rtd_theme#788

https://stackoverflow.com/questions/46269345/embed-plotly-graph-in-a-sphinx-doc

@dcfidalgo could you take a quick look when you have some free slot?

[dcfidalgo]

@frascuchon I see some new commits, did you manage to solve this issue?

[frascuchon]

All related work will be done in #544