create method
Create the initial data structure.
Implementation
@override
create() => <String, Map<String, dynamic>>{
'CharacterClasses': <String, CharacterClass>{},
'Items': <String, Item>{},
'Monsters': <String, Monster>{},
'Moves': <String, Move>{},
'Races': <String, Race>{},
'Spells': <String, Spell>{},
'Tags': <String, Tag>{},
};