Implement Youtube connector

[tahpot]

Implement Youtube handlers in the Google provider.

Phase 1:

User the facebook/following.ts and the google/gmail.ts files as examples to following when building the Youtube handler.

• Create a new youtube-following.ts handler within the existing Google provider
• Map Youtube subscriptions data to the Verida following schema (https://common.schemas.verida.io/social/following/v0.1.0/schema.json) See facebook/following.ts for example.
• Add the necessary youtube scopes to the existing Google provider getScopes() method.
• Add a getYoutube() method into the youtube-following.ts library to instantiate a connection to the Youtube library.

Then, let's have another call to work on next steps.