[Rd] New grDevices::hcl.colors()

[Achim Zeileis]

Hi everyone,

I wanted to draw your attention to a new post on the 
developer.R-project.org blog:
https://developer.R-project.org/Blog/public/2019/04/01/hcl-based-color-palettes-in-grdevices/

A new function grDevices::hcl.colors() greatly extends the color palette 
functionality available in base R. Also, the defaults in the heatmap 
functions image() and filled.contour() have been adapted accordingly.

Feedback is welcome, especially regarding potential problems with the 
changed defaults.

Best wishes,
Z