feature: embedded tweets

[invisiblegaudi]

Problem:

Related to #122

When outputting HTML, it is desirable to embed tweets rather than have a link to them taking the reader away from the page.

Solution:

I would like to have a flag e.g. --embed-socials to add the necessary HTML and js around the links to embed any urls to tweets

[invisiblegaudi]

willing to do the work for this

[simonhaenisch]

Closing as a duplicate of #233 because it's basically the same thing but just for a different social platform.

See #233 (comment), imo best idea for it is to be solved with custom Marked extensions that can be published as npm packages, and we just need to make it easier to use those in md-to-pdf.