Need new embed type for Opinary

[brandonhundt]

Opinary lets you embed pre-made widgets into posts from their service. This would need to be a new embed type in the admin. Ideally, all an editor needs to do is add is the URL to the widget through the embed. example of embed code directly from Opinary dashboard:

<div class="opinary-widget-wrapper" style="width: 100%; max-width: 1200px; height:100%; margin:0 auto;"> <div class="opinary-widget" style="position:relative; padding-top: 100%;"> <iframe class="opinary-iframe" src="https://compass.pressekompass.net/compasses/pri/does-this-put-you-off-flying-with-united-afe4" style="position: absolute; top: 0; left: 0; width: 100%; height: 100%" frameborder="0"></iframe> </div></div><script src="//compass.pressekompass.net/static/opinary.js"></script>

HOLD STATUS: Wait until we are confident these will be used.

[brandonhundt]

Container placeholders in place with this PR: #388

@lukasgit We will need to establish an endpoint for embeds with the object type of "opinary"

Fields: Title, Source (both required)

Thanks!