Restoration ID to save and restore the scroll offset of the EditableText.
If a restoration id is provided, the EditableText will persist its current scroll offset and restore it during state restoration.
The scroll offset is persisted in a RestorationBucket claimed from the surrounding RestorationScope using the provided restoration ID.
Persisting and restoring the content of the EditableText is the responsibility of the owner of the controller, who may use a RestorableTextEditingController for that purpose.
- RestorationManager, which explains how state restoration works in Flutter.
final String? restorationId;