Link replacement

[Rich-Harris]

JSDoc snippets often include links to https://kit.svelte.dev/docs/whatever, because we want the links to be valid inside editor tooltips. But these also get rendered as-is on the site itself. That's fine in production, but a (minor) nuisance for preview deployments.

It might be good if there was an option for replacing links — something like this:

import { VERCEL_URL } from '$env/static/private';

const base = 'https://kit.svelte.dev/';

renderContentMarkdown(filename, body, {
  ...stuff,
  transformLink: (href) => href.startsWith(base)
    ? href.replace(base, `https://${VERCEL_URL}/`)
    : href
});