I know I'm super late to the party. But hey, let me! I just inject this on the very same page, and also start to insert HTML paragraph with some styling on it and as easy as that, I can literally do extensive amount of HTML work on this post.

<link href='https://fonts.googleapis.com/css?family=Bangers' rel='stylesheet'>

What you can put in your editor:

<p style="font-family:'Bangers';text-align:center;">Kapoow!</p>

It's a Bird... It's a Plane... It's Superman

And of course I can do something like hover effects, snow, rain and plenty other CSS & JS stuff.