Define the type of a route

Following @Vinnl_gitlab [suggestion](https://gitter.im/solid/chat?at=5e5cc3227fef7f2e89968763), a good way that apps can discover routes in solid pods is through the [Type index registry](https://github.com/solid/solid/blob/master/proposals/data-discovery.md#type-index-registry). In order for that, it will be important to put special care on a type for routes.

Some questions:

- Is there any commonly accepted type?
- Otherwise, which one would be a good name? `viade:Route` ? Assuming we already have a `viade` namespace?

Start with the linked Solid Type Index Registry section in data-discovery.md and review how the Viade data model defines namespaces. Investigate whether a commonly accepted route type exists and compare it with the proposed viade:Route name. Done means the specification records a decided route type and namespace for app discovery.

Written by the indexing model from the issue text.