#8 Refactor/upgrade to bevy 0.18 (and other dependencies)
- Upgrade bevy from 0.9.1 to 0.18.1
- Upgrade bevy-inspector-egui from 0.14.0 to 0.36.0
- Upgrade wasm-bindgen / wasm-bindgen-cli from 0.2.86 to 0.2.114
- Remove iyes_loopless in favor of native Bevy state management
- Migrate to Bevy 0.18 APIs (Messages, ButtonInput, Node-based UI, AudioPlayer, TextureAtlasLayout)
- Add touch input support for spawning enemies on mobile