Add ColorSequence and Plotly Express qualitative color sequences

Add plotly::color::qualitative with ColorSequence (len, modular get,
reversed) and all 19 px.colors.qualitative sequences plus reversed
*_R variants, sourced from plotly.py 7.1.0.

Fixes #396

Author: iynehz

CHANGELOG.md

@@ -20,6 +20,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/) a
 - [[#422](https://github.com/plotly/plotly.rs/issues/422)] Add `Indicator`, `Histogram2d`, `Icicle` trace types 
 - [[#425](https://github.com/plotly/plotly.rs/issues/425)] Add `Splom` and `Parcats` trace types (scatter-plot matrix and parallel categories) 
 - [[#432](https://github.com/plotly/plotly.rs/issues/432)] Add `Funnel` and `Waterfall` trace types
+- [[#396](https://github.com/plotly/plotly.rs/issues/396)] Add `ColorSequence` and Plotly Express qualitative color sequences (`plotly::color::qualitative`), including reversed (`*_R`) variants
 
 ### Changed
 

plotly/src/common/color.rs plotly/src/common/color/mod.rsplotly/src/common/color.rs renamed to plotly/src/common/color/mod.rs

@@ -1,3 +1,5 @@
+pub mod qualitative;
+
 use std::error::Error;
 use std::fmt;
 use std::num::{ParseFloatError, ParseIntError};
@@ -20,6 +22,9 @@ use std::str::FromStr;
 /// to their own requirements. On the whole, that should be largely unnecessary
 /// given the functionality already provided within this module.
 ///
+/// Discrete color sequences from Plotly Express are available in the
+/// [`qualitative`] module.
+///
 /// [`CSS color formats`]: <https://www.w3schools.com/cssref/css_colors_legal.asp>
 /// [`predefined colors`]: <https://www.w3schools.com/cssref/css_colors.asp>
 use dyn_clone::DynClone;