New docs site

Planning issue to discuss what we're looking for in a new docs site.

• Things we should keep
  • Live editable code examples
  • Runtime theme loading/switching
  • Usage guidelines
    • Opportunity to improve as we go
• Things we should add
  • Real-world examples
    • Like usage insights but better
      • With frontend-base converted frontend apps we might be able to do this by importing components from npm published apps.
  • Recommended ways to use something (in comparison to all the different ways it is used throughout frontend apps)
    • Clear distinction between human recommendations and machine gathered usage data
      • How to classify? Way to say "this is good, we should consider how to better support this in/with paragon" and "we haven't looked at this, we should see if this is a bad pattern we should try to replace" etc.
• Things we should change
  • Structure (follow atomic design hierarchy)
• Things we should remove
  • //todo

Other thoughts:

• What "wrapper" components in frontend apps are good vs bad
  • Wrapping a Paragon component to set props to keep an app more DRY is fine
  • classnames
    • using for "reasonable" things like adding margin/padding (basically any bootstrap helper classes) makes sense
    • things can get messy with custom css overriding (!important) Paragon component styles
    • https://github.com/openedx/paragon/issues/3785
  • Popover vs modal
    • https://github.com/openedx/paragon/pull/3777

This is a planning issue; no implementation files, tests, or entry points are named. Start by reviewing the listed keep/add/change/remove goals and the linked Paragon issue #3785 and pull request #3777. Done is an agreed scope and structure for the new documentation site, not a defined code change.