feat(Theming): add color palette

[layershifter]

Fixes #423.

[layershifter]

This PR will be never merged. Using it to prove some ideas.

[codecov]

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Impacted Files	Coverage Δ
src/components/Divider/Divider.tsx	100% <ø> (ø)

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[kuzhelov]

I am reading this as a client, and have a reasonable question: text color is largely influenced by the backgeround where text is used, but thjis paragraph suggests that there is only single text color suggested (yes, maybe with several tints, but still just a single color) - and this contradicts most approaches to color palette where text color is largely defined by the background - and, thus, on variants for text color (generally - content color, such as text, icons, etc) are suggested: onPrimary, onSecondary, etc. More than that, depending on the tint of the background different text color might be used, so that content will appear with enough visual contrast.

What is our suggestion here?

[kuzhelov]

also, might suggest to rename it to something that is more generic than text, as this color generally applies not only to text content

[kuzhelov]

one thing that I still missing, even after reading the guide, is what are the steps I should follow as a client to introduce color palette to my theme? What are the tools that will aid me in that? If it is not the purpose of this PR - please, let me know what are our steps planned to address that?