Create a loading animation

[jenweber]

Over low data connection speeds, the experience while waiting for content to load is not great.

We should implement a loading animation.

[mansona]

I've solved this issue in ember-learn/guidemaker-ember-template#4 👍

It's not really an issue with empress/guidemaker and more so something that the individual templates can decide to add 👍

This is a bit of a reminder that I need to write the Guidemaker Architecture blog post 😂