Add extension point for freestyle-dynamic input to use a custom component

[lukemelia]

Perhaps something like:

{{#freestyle-dynamic 'rating-group-some'
    dynamicProperties=(hash score=(hash value=3.5 component='slider' options=(hash min=0 max=5)))
    title='Rating Group - Some stars'
    componentName='rating-group'
    as |dynamic|
  }}
    {{rating-group score=dynamic.score}}
{{/freestyle-dynamic}}

(specifically the component prop passed as part of the dynamicProperties hash)