Playground: Add sandboxed iframe

[ajhager]

Replace 'generated code' pane with an iframe the program is injected into. This way, the user can experiment with dom manipulation without interfering with the appearance and functionality of the playground itself.

Also add fullscreen button that overlays the iframe on top of the playground with full width and height of the page.

[dmitshur]

Also add fullscreen button that overlays the iframe on top of the playground with full width and height of the page.

What does this mean and what is it for?

[ajhager]

They press run, and the consequences show up in the iframe. The user might then want to be able to see the iframe maximized a bit. So perhaps the button expands the iframe to 90% - 100%. They can then explore their demo in a more spacious and typical environment.

[dmitshur]

Gotcha.