message: chore: add mention of snapshot format change in upgrade guide
diff: @@ -14,3 +14,16 @@ See [changelog](https://github.com/facebook/jest/blob/main/CHANGELOG.md#2900) fo
  ## Compatibility
  The supported Node versions are 14.15, 16.10, 18.0 and above.
  +
  +## Snapshot format
  +
  +As announced in the [Jest 28 blog post](/blog/2022/04/25/jest-28#future), Jets 29 has changed the default snapshot formatting to `{escapeString: false, printBasicPrototype: false}`.
  +
  +If you want to keep the old behavior, you can set the `snapshotFormat` property to:
  +
  +```diff
  ++ snapshotFormat: {
  ++ escapeString: true,
  ++ printBasicPrototype: true
  ++ }
  +```
  