Add TETR.IO (#2766)

README.md

@@ -814,6 +814,7 @@ API | Description | Auth | HTTPS | CORS |
 | [SuperHeroes](https://superheroapi.com) | All SuperHeroes and Villains data from all universes under a single API | `apiKey` | Yes | Unknown |
 | [TCGdex](https://www.tcgdex.net/docs) | Multi languages Pokémon TCG Information | No | Yes | Yes |
 | [Tebex](https://docs.tebex.io/plugin/) | Tebex API for information about game purchases | `X-Mashape-Key` | Yes | No |
+| [TETR.IO](https://tetr.io/about/api/) | TETR.IO Tetra Channel API | No | Yes | Unknown |
 | [Tronald Dump](https://www.tronalddump.io/) | The dumbest things Donald Trump has ever said | No | Yes | Unknown |
 | [Universalis](https://universalis.app/docs/index.html) | Final Fantasy XIV market board data | No | Yes | Yes |
 | [Valorant (non-official)](https://valorant-api.com) | An extensive API containing data of most Valorant in-game items, assets and more | No | Yes | Unknown |