Add sidebar to Ember example

[flashdesignory]

Some newer examples did have a missing sidebar, which most of them were added back in this pr: #2254

Could we bring back the sidebar for the Ember example as well?

https://todomvc.com/examples/emberjs/todomvc/dist/

@NullVoxPopuli - is this something that you might be interested in adding? 😄

[NullVoxPopuli]

what's the sidebar look like? does it have markup requirements?

[flashdesignory]

An example can be found here: https://todomvc.com/examples/knockoutjs/

It's part of the todomvc.com website and just gets injected in your build.
It just shows up if you run the todomvc.com website locally, and won't affect the todomvc build.

couple steps needed:

1. npm install todomvc-common
2. inject the css somewhere:
3. inject the js file somewhere: <script src="node_modules/todomvc-common/base.js"></script>
4. update this file as needed: https://github.com/tastejs/todomvc/blob/master/learn.json

To preview, you'd need to run the todomvc website from the root.

That's pretty much it. Happy to help / review prs.
This would be super helpful 😄