New Feature: Color Palettes

[kezoponk]

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

I know you have the bg-opacity and other things but I have a great idea:
Make a couple of more related colors to the current ones, and document how these are greatly combined. Or name them as the palette so that you should only combine them with the same palette, ex warning-joy, secondary-joy & dark-joy

Example:
bs-dark goes very with (brighter)#393e46 and (brightest)#596067

Motivation and context

This would make bootstrap a standard to follow and also be helpful for people just getting into designing and don't yet know anything about palettes and why they're so important

++ A nice page in bootstrap documentation about the different palettes would make it so much easier to decide which palette to use for the new project

[mdo]

#35857 should help with this.