WIP: Create an Object page template for Pajamas

We've started documenting objects in Pajamas (see the MR object). Currently we don't have any contribution guidelines for documenting objects. For someone unfamiliar with the purpose and process of object modeling it can be intimidating and difficult to get started.

The conceptual object model becomes more useful as more objects and layouts are documented since it helps communicate the relationships between different objects. The more objects and layouts we document (even if the model is imperfect at first), the more we'll be able to use it. For example, it can help identify important object relationships and ensure we don't overlook them in our design work.

We don't need to create a perfect set of guidelines and templates to start benefiting from the documented model. The objective is to create an MVC set of guidelines and resources to get more product designers interested in contributing.

Relates to #1150 (closed)