Example: Fullscreen and Maximize

[bryphe]

I'd like to add an example that highlights the Fullscreen and Maximize capabilities of the framework.

We already have a Window.maximize API - so that piece would be easy to hook-up.

Glfw also has the capability to create a 'full-screen' window - we need to hook up those APIs completely in reason-glfw: https://github.com/bryphe/reason-glfw/issues/58 but once we have that - we can add a wrapper around those raw GLFW APIs on our Window API like Window.toggleFullscreen.

The example itself would be relatively simple:

• A button labeled Maximize. When clicked, this would call Window.maximize, and change state to be labeled Restore. When clicked, this would restore the Window to its pre-maximized dimensions (we might need a new API for this!)
• A button labeled Start Fullscreen. When clicked, this would call Window.fullscreen. Ideally, we could detect the full-screen state and change the label to Stop Fullscreen.

This would be a good exercise and demonstration of the windowing behavior of Revery on different platforms.