Disable Bevy renderer for tests

Building a bevy crate to ease 2D sprites animations, we wanted to use some parts of the SpritePlugin crate (precisely the TextureAtlas) which deeply rely on the RenderPlugin.

Opening a window and testing rendering is not possible in tests/CI environments, which seems logic. So we needed to disable all these features to make our test pass.

Here is a basic code to run your Bevy app with no renderer and no window:

#[test]
fn sprite_time_is_updated() {
    // Setup app
    let mut app = App::new();

    app.add_plugins(DefaultPlugins
        .build()
        .set(RenderPlugin {
            render_creation: WgpuSettings {
                backends: None,
                ..default()
            }
                .into(),
        })
        .disable::<WinitPlugin>());

    // Now you can run your tests
}