v0.1.5 of firestore_builder

The easiest way to integrate Firestore into a Flutter application Changelog excerpt: - Add the `unknown_enum_value`field option: emits `JsonKey(unknownEnumValue: ...)`so unknown enum values decode to a fallback instead of throwing. - Fix the generation of `UpdatedValue`classes for `List`and `Map`of custom classes (`List `produced an invalid class name), and share one class between a custom class…