Spent some time working through this, and it proved to be more challenging that originally anticipated. Much of this is because we're using static generation, and the point of this feature is that we want to introspect the URL based on the request, extract the global content id, and use that to find the appropriate page.

Therefore, I'm going to take a bit of a different approach here:

• Switch to server-side rendering
• Identify the doc by the ID in the URL as the value after the last - before a ? or trailing slash/hash.
• If the request URL doesn't match url_path, redirect to or rewrite the appropriate URL path.
• Add an exception for /docs, which should render the docs index page, as this should never change.
• Consider a better way to handle breadcrumbs. Having a reference at CL build time may make this easier, but not sure what's possible here.
• Similar considerations for active nav items. Ideally we'd use the current doc ID, but let's investigate to see if there's an easier way.

fixes #33
fixes #101