feat: improve support for dubbed content

[LuanRT]

Description

The goal of this PR is to make it easier to identify and extract the audio tracks of videos with multilingual audio. I'm also considering adding an option to filter out unwanted formats from the DASH manifest and download function, which is why this is a WIP. (done)

Usage

import { Innertube, UniversalCache, YTNodes } from 'youtubei.js';

(async () => {
  const yt = await Innertube.create({ cache: new UniversalCache(), generate_session_locally: true });
  
  const search = await yt.search('mrbeast I Survived 50 Hours In Antarctica', { type: 'video' });
  const video_id = search.results?.firstOfType(YTNodes.Video)?.id as string;

  const info = await yt.getInfo(video_id);
  
  // Remove unwanted formats from the DASH manifest:
  console.log(info.toDash(undefined, (fmt) => {
    // Remove all non-English audio tracks (the data in info.captions.audio_tracks is quite helpful for this specifically)
    if (fmt.language && fmt.language !== 'en')
      return true;
    return false;
  }));

  console.log(info.toDash(undefined, (fmt) => {
    // Remove all dubbed audio tracks
    if (fmt.is_dubbed)
      return true;
    return false;
  }));

  // Download a specific audio track:
  const stream = await yt.download(video_id, {
    type: 'audio', language: 'hi' /** Default: 'original' */
  });

  // ...
})();

Type of change

• New feature (non-breaking change which adds functionality)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings