Update for more modern rust and add some features

[worikgh]

It has been a long time since simple was updated. I have found it very useful. I have added full-screen windows and cleaned up the code.

• Rust edition 2024
• Took clippy's advice to suppress warnings
• Add a full screen constructor for the Window
• Add pub fn drawable_size() -> (u32, u32) to Window
• Add a test for drawable_size
• Make the examples squares and city use full-screen windows