Implement experimental XPFF and x-client-transaction-id support

[karashiiro]

Adds experimental (largely untested) support for generating the xp-forwarded-for and x-client-transaction-id headers.

Enable this with the new experimental options on the Scraper instance:

const scraper = new Scraper({
  experimental: {
    xClientTransactionId: true,
    xpff: true,
  },
});

This PR also logs a debug event and simply continues if guest token activation fails. On the website, I'm currently seeing that /activate.json hits 429s on almost every single request, and there are no guest token headers or cookies, yet it's still possible to access the TweetResultByRestId endpoint. I'm taking this to mean that it may not be required anymore, or at least not in all circumstances.

[karashiiro]

#165