message: docs: Add React 18 Upgrade to v8 upgrade guide
  Resolves:
  This will add information about React 18 Upgrade to v8 Upgrade guide
  [category:Documentation]
diff: @@ -78,7 +78,19 @@ above will no longer run in IE11 and will fail to bootstrap with an error and/or
  ### React 18 Upgrade
  -> Coming Soon (https://github.com/Workday/canvas-kit/discussions/1545)
  +We've upgraded Canvas Kit to [React 18](https://reactjs.org/blog/2022/03/29/react-v18.html). This
  +change will not impact users who are already on v7 and are looking to upgrade to v8 as v8 will
  +support the same React versions as v7 (React 16.14 and 17.X) while still giving them the ability to
  +upgrade to React 18 as needed. Although we didn't use any new features from React 18 in v8, _future_
  +updates to Canvas Kit may require upgrading to React 18 to support them.
  +
  +React 18 introduces several new features, but the most impactful change is the new
  +[concurrent render API](https://reactjs.org/blog/2022/03/29/react-v18.html#what-is-concurrent-react).
  +The new `createRoot` method replaces `render` and gives you access to the improvements in React 18
  +including the concurrent features. Without it, React behaves as it did in previous versions.
  +
  +See our [React 18 discussion](https://github.com/Workday/canvas-kit/discussions/1545) for more
  +information.
  ---
  