Create a "webpage" wrapper for around images

[mansona]

In the guides we now have images that have a very similar background colour as the guides themselves e.g. https://guides.emberjs.com/release/tutorial/part-1/orientation/

We should have some way to "wrap" these images in a browser window, keeping in mind this needs to work somehow with Markdown so we may need to implement some custom showdown extension for it 👍

[MelSumner]

@mansona can you clarify- do you want some CSS to add a border or similar, or an actual component or div element wrapper?

[mansona]

So it needs to work in a markdown context so I would suggest that it needs to be a CSS class or just some plain HTML and CSS that we can add when we know we need it from a showdown extension 🤔 i.e. it can't be an Ember Component 👍