Function register_asset_loader 

pub fn register_asset_loader(app: &mut App, loader: impl AssetLoader)

Registers an AssetLoader from a plugin’s build, installing the AssetServer first if this plugin runs before AssetsPlugin.

struct QoiPlugin;

impl Plugin for QoiPlugin {
    fn build(self, app: &mut App) {
        lumen_assets::register_asset_loader(app, QoiLoader);
    }
}