feat: update website & init template palette to pass WCAG test; include contrast check in ColorGenerator (#5822)
* docs: update website palette to pass WCAG test
* Darker palette in light mode
* Fix CodeBlock
* Fix front page
* Fix announcement color
* Unify primary color
* Add contrast check in website
* Fix color input not updating
* Use website for preview; allow changing background
* Persist in localStorage
* Fixes
* Fix SSR
* Edit dark mode separately
* Fix light mode palette
* Fix storage reset
* Fix CSS
* Fix
* fix toggling when not on styling-layout
* require 100% lighthouse accessibility score
* use sessionStorage
* refactor
* tweak light color
* update comments
Co-authored-by: sebastienlorber <lorber.sebastien@gmail.com>
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