Framework specific page redirects

Some pages will be so different from Angular and React that they'll need entirely different pages and markdown files. The router should be able to redirect to the appropriate page for these special routes.

For example, `/docs/navigation` should be able to redirect to `/docs/navigation/angular` or `/docs/framework/react` automatically.

More thought needs to be done around how to handle Google bots and non-js browsers on these pages, probably showing an index page of possible sub-pages.