[Feature]: Create a customizable Figma plugin for DT palette generator

[kpanot]

Context

To accelerate the design and the definition of a new theme for a customization, a Figma Plugin is required.
A first version of a plugin has be delivered on #2870. This first version require the usage of a third party plugin and does provide, without visualization, an hardcoded kind of palette.

The purpose of this task is to improve the Figma plugin delivered.

Proposal

The plugin should response to the following technical criteria :

• Be based on Angular
• Using Figma UI Components (cf. https://www.figma.com/plugin-docs/figma-components/)
• Expose function properly unit tested

The plugin should offer the following options :

• Option to determine the number colors in the palette (and their level)
• Option to determine the scale of the colors
• Option to determine a regex list of the collections (Variable list) to consider as Palette

The plugin should provide the following feature :

• Selection of the palette to edit/regenerate (the value of the variable should be loaded when selected)
• Visualize the full generated palette based on the middle color (usually 50)
• Offer the possibility to override each color of the palette
• Possibility to create a new collection (and its variables) instead of editing an existing palette