Scaffold out Freestyle::Usage with support for :example named block

[chrislopresto]

Make something like this:

<Freestyle::Usage @title='More List Icon'>
  <:example>
    <MoreList
        @morePages={{this.morePages}}
        @drillDown={{fn @logAction 'MoreList drillDown'}}
    />
  </:example>
</Freestyle::Usage>

[lukemelia]

Scaffolded in #380

[lukemelia]

Implemented in #457