Bevy 0.18 release

// This program demonstrates that Bevy 0.18 is a new crate version.
// It does not compile against the current sandbox because the crate
// is not available here, but it shows how you would use it in a real
// project.

fn main() {
    // In a real project you would add `bevy = "0.18"` to Cargo.toml
    // and then write something like:
    //
    // use bevy::prelude::*;
    //
    // fn main() {
    //     App::new()
    //         .add_plugins(DefaultPlugins)
    //         .run();
    // }
    //
    // For this sandbox we simply print a message.
    println!("Bevy 0.18 has been released.");
}