New documentation

[nstepien]

• API documentation
  • We'll probably write all the API docs in the README.md
  • Prepare API documentation skeleton #2615
  • Document Column - summaryRowHeight, rowRenderer #2650
  • API Documentation in README #3904
  • Expand styling and customization docs #3933
  • Review docs #3959
• Examples / demos
  • Remove the old docs
    • swap canary <-> old #2653
    • Tweak storybook deployment #2648
    • Replace storybook #2655
  • We need to review the examples we have, polish them, and see if they're relevant/pertinent
• Update the description field in package.json package.json: Tweak description (#2575) #2644
• https://github.com/adazzle/react-data-grid/community
  • Add one or more issue templates
    • Add bug report template #2645
    • Add Feature request issue template #2649
  • Add a pull request template?
• README.md
  • Review badges
  • Review links
  • Review installation guide README: Trim install section #2646
  • Review quick start README: Trim install section #2646
  • Features list README: add features list (#2575) #2642
  • List browser / react support README: add features list (#2575) #2642
  • Performance Considerations
• CONTRIBUTING.md
  • How to develop
  • How to test
  • How to contribute
• Write change logs up to a stable 7.0.0 release