MAL Sync integration

I'm requesting MAL Sync to add support for Bangumi but they need the following APIs to be implemented. Detailed discussions can be found at [MALSync/MALSync#792](https://github.com/MALSync/MALSync/issues/792).

> lolamtisch commented on Jul 9
>
> This should prety much be all informations needed per api call.
>
> ```
> Single Entry
> internalId: any
> malId: number
> type: 'anime' | 'manga'
> url: string
> userStatus: 'watching' | 'pantowatch' | 'completed' ....
> userScore: any
> userWatchedEpisode / chapter: number
> userWatchedVolumens: number
> totalEpisodes: number
> totalVolumes: number
> image: string
> globalScore: any
>
>
> // possible to filter by userState
> list[]
> internalId: any
> malId: number
> type: 'anime' | 'manga'
> title: string
> url: string
> totalEp: number
> userWatchedEpisode / chapter: number
> userStatus: 'watching' | 'pantowatch' | 'completed' ....
> userScore: any
> image: string
>
> Search[]
> id: number;
> name: string;
> altNames: string[];
> url: string;
> image: string;
>
> Overview metadata:
> Just metadata not important
> ```

No files, tests, or entry points are named in the issue. Start by reading the linked MALSync/MALSync#792 discussion and comparing the server's existing API patterns. Done means the requested Bangumi single-entry, list, search, and metadata APIs support the fields and filters described in the issue.

Written by the indexing model from the issue text.