Type `Config` exported from `validated-changeset/dist/types` is missing the `changeset` key

According to [this ember-changeset doc](https://github.com/poteto/ember-changeset#extending-the-base-ember-changeset-class), we can specify the class of the Changeset we want to use when building a changeset.

I believe the type [Config](https://github.com/validated-changeset/validated-changeset/blob/main/src/types/index.ts#L11), which contains two optional keys at the moment (`skipValidate` and `changesetKeys`), is missing the third key `changeset`