Add support for embedding videos

[Son H. Mai (Mason)]

While we can embed videos using HTML like this:

<iframe width="560" height="315" src="https://www.youtube.com/embed/dQw4w9WgXcQ?si=n1PmPV5KwExea0aZ&amp;controls=0" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

It's cleaner to just use the video ID or URL:

@[youtube](dQw4w9WgXcQ)
@[vimeo](https://vimeo.com/347119375)

[Son H. Mai (Mason)]

As per comment #36 (comment)
Closing this issue as not planned.