README: Add an introductory video

[davidfstr]

Make a video introducing how to use Crystal (and not just rely on the walls-of-text in the current tutorial).

Prerequisites:

• [ ] https://daarchive.net/ home page has an initial design for linking to archived websites that I post online
  • Hero image at the top, of a library bookshelf (because it's an "archive")
  • List of available archived sites that links to each appropriate subdomain
    • Perhaps formatted as a book turned sideways with the name of the website on the book's spine
  • Bonus: If you click a book, it animates turning the cover to face the viewer, opens the book, and reveals a title page explaining what the site is, perhaps with a small image of the site's home page. Think: "Myst book".
• [ ] https://xkcd.daarchive.net has an archived version of xkcd.com so that there is an example website to download (which isn't a real site that could get swamped by traffic)

See also:

• CATHODE: 2021-03-26#2 - Sizzle Video Script.txt
  • Early thoughts on what might be in such an intro video.