Comment 4 for bug 1243248

<div data-role="mainview"> has no JS obect in UbuntuUI.

This means that the design.ubuntu.com page that discusses mainview CAN provide a link to docs for QML but cannot for JS.

Let's add a mainview object and provide some minimal docs description of it so that devs know they need it, where it must be (child of body) and etc.