This theme component will rewrite links to stuff like digitalocean.com, http://bunny.net, and www.massive.io with your referral links! Something similar might be done with watched words, but this works all in the browser, so you don’t need to rebake when you change or add new links.
The regex matches http and https as well as optionally adding www.
Mouse over the links to see the referral address. See the raw markdown to see that it’s just the auto-linked hostnames that I typed!