Add mangadex (#2069)

README.md

@@ -135,6 +135,7 @@ API | Description | Auth | HTTPS | CORS |
 | [AnimeNewsNetwork](https://www.animenewsnetwork.com/encyclopedia/api.php) | Anime industry news | No | Yes | Yes |
 | [Jikan](https://jikan.moe) | Unofficial MyAnimeList API | No | Yes | Yes |
 | [Kitsu](https://kitsu.docs.apiary.io/) | Anime discovery platform | `OAuth` | Yes | Yes |
+| [MangaDex](https://api.mangadex.org/docs.html) | Manga Database and Community | `apiKey` | Yes | Unknown |
 | [MyAnimeList](https://myanimelist.net/clubs.php?cid=13727) | Anime and Manga Database and Community | `OAuth` | Yes | Unknown |
 | [NekosBest](https://docs.nekos.best) | Neko Images & Anime roleplaying GIFs | No | Yes | Yes |
 | [Shikimori](https://shikimori.one/api/doc) | Anime discovery, tracking, forum, rates | `OAuth` | Yes | Unknown |