Add sequential and diverging palettes

[Nate Baldwin]

Add support for sequential and diverging palettes.

Each type would need unique configs for setup. Sequential would need:

• Shift input (exponential slider)
• Clamping option (full black/white or only key colors)
• Number of colors to output

Diverging would need:

• Shift input
• Clamping
• Number inputs
• Unique gradient & separate inputs for each side of the diverging scale

See branch: https://github.com/adobe/leonardo/blob/sequential-colors/packages/ui/src/index.js

[Nate Baldwin]

Here is a prototype for sequential scale manipulation: https://codepen.io/NateBaldwinDesign/full/mdJqKpP

Features:

1. Clamping color values to input only
2. No clamping = adds black & white to color scale
3. Correct lightness = implements Leonardo's current method of dynamic domains based on key color lightness values.
4. No corrected lightness = simple implement by which each color is equally spaced in the domain range.

[Nate Baldwin]

Current WIP on this branch fails tests by single hexidecimal values due to update in method for outputting colors (incrementally rather than using d3.range() function)