message: docs(migrate-6): add "Requirements changed" section
diff: @@ -9,6 +9,11 @@ These are the changes made for 6.0.0 that are breaking or just important to know
  This Guide is written for migration from version `5.9.2` to `6.0.0`, for versions `>6.0.0 <7.0.0`, please consult the [CHANGELOG](https://github.com/typegoose/typegoose/blob/master/CHANGELOG.md)
  :::
  +## Requirements changed
  +
  +- Typescript `3.5` is now required / recommended
  +- Mongoose `5.7.1` or higher is now required
  +
  ## InstanceType changed
  `InstanceType<T>` was renamed to `DocumentType<T>`
  