Function onChildAdded

database/useList.ts:29–34

(
      snapshot: DataSnapshot | null,
      previousKey?: string | null
    )

    }

    const onChildAdded = (
      snapshot: DataSnapshot | null,
      previousKey?: string | null
    ) => {
      dispatch({ type: 'add', previousKey, snapshot });
    };

    const onChildChanged = (snapshot: DataSnapshot | null) => {
      dispatch({ type: 'change', snapshot });