Add `MusicClient`

[SuspiciousLookingOwl]

Is your feature request related to a problem? Please describe. Music client (used on music.youtube.com) seems to have different search algorithm compared to youtube.com, and can be more suitable if you need to search for a music specifically, and not a video. It also has slightly faster search response compared to youtube.com (around 200-300ms faster)

Describe the solution you'd like Create a MusicClient with basic functionality like .search and .getMusic

import {Client, MusicClient} from "youtubei";

const client = new Client(); // YouTube Normal Client
const musicClient = new MusicClient(); // YouTube Music Client

[SuspiciousLookingOwl]

Added on https://github.com/SuspiciousLookingOwl/youtubei/commit/9b62e305e144ddba4dc10ddfd8dae7d07e937fec

With 2 API:

• .search(keyword)
• .getLyrics(id)

More API to come