fix: update DatedUserAchievement model to be an object

[minhaferzz]

When calling getAchievementsEarnedBetween() and getAchievementsEarnedOnDay() the returned type is Promise<DatedUserAchievement[]>.

DatedUserAchievement is defined as:

export type DatedUserAchievement = {
    date: string;
    hardcoreMode: boolean;
    achievementId: number;
    title: string;
    description: string;
    badgeName: string;
    points: number;
    author: string;
    gameTitle: string;
    gameIcon: string;
    gameId: number;
    consoleName: string;
    cumulScore: number;
    badgeUrl: string;
    gameUrl: string;
}[];

This means the promise would return an array of arrays. This PR updates DatedUserAchievement to be simply an object so it is consistent with what the API returns.

[wescopeland]

Thanks 👍 I will get this into a release.