feat(Session): allow setting a custom visitor data token

[LuanRT]

Description

Adds a new option to allow custom visitor data tokens. Note that it must be a valid token.

Usage

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

(async () => {
  const yt = await Innertube.create({ 
   cache: new UniversalCache(),
   generate_session_locally: true, 
   visitor_data: '...'
  });
})();

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

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