Technique F110: Add screenshots to help the user see examples

[ljoakley]

In technique F110, we have two Failure examples, sticky footer and sticky header. Would it make sense to add a couple of screen shots to help the users understand what would be a failure?

[mbgower]

Please feel free to submit some screenshots as a PR. I suspect it will take more than one to properly illustrate something of this dynamic nature. A working example is another option.

[ljoakley]

I think that a working eampe would be great. I would need someone to create this as I have no idea how to do this.

[giacomo-petri]

I can take this one