Make a Color Scale page, remove Color Scale examples in Heatmap pages

[etpinard]

Heatmap doc pages take quite a bit of time to load e.g. for python and even worse for matlab.

This makes me reluctant to add more Heatmap examples to the docs e.g. this one.

I suggest we make new page, one for each API, dedicated to color scale (custom, pre-defined, used in conjunction with 'zauto', 'zmin' and 'zmax', etc.).

Plotly color scales can be used not only in Heatmap, but also in Contour, Histogram2d, Histogram2dContour and Scatter (and hopefully Bar and Histogram soon). So why hide this info in the Heatmap doc page?

The color scale doc page could be placed under Layout as a quick fix that does not require reorganization (although this is far from ideal as 'colorscale' is a trace key).

Perhaps we could make a new section on colors, combing the color scale page with a page on color formating (as mentioned in this Asana task).

[theengineear]

(1) yes. a separate page for colorscale definitely makes sense.
(2) should we make the z matrix smaller for the heatmaps page? Wouldn't be terribly hard.