Show how to add custom buttons

[nichtich]

Right now all buttons used in the example are hard-coded. In practice you want some custom buttons and input fields in your application and some buttons like "'about' make no sense for other applications but the demo page. The documentation should show how you can add custom buttons, exemplified by the "about" button.

[jagthedrummer]

Hey Jakob, thanks for opening this issue. It's going to take a bit of refactoring to get everything to a state where this is possible, but it definitely needs to be done. It'll probably be at least a few weeks before I have a chance to get into it, but I'd be more than happy to merge some changes in the mean time.

Thanks again for getting involved.

Jeremy