[pbr] Create a DirectionalLightBundle

[dannymcgee]

Objective

• Fixes add DirectionalLightBundle similar to PointLightBundle #2184

Solution

• Created a DirectionalLightBundle in bevy_pbr with Transform and GlobalTransform components
• Added the DirectionalLight component to the PbrPlugin's registered types
• Updated the 3d_scene example by replacing the PointLightBundle with the DirectionalLightBundle*

*I tried to keep the appearance of the lighting pretty close to the original scene, so the only real difference should be that the new light doesn't have any fall-off. But I could create a new example instead if that would be preferred.

[mockersf]

bors try

[bors]

try

Build failed:

• build (stable, ubuntu-latest)

[cart]

Normally I would merge this because it is relatively uncontroversial and provides useful functionality, but we are planning on overhauling bevy_render prior to 0.6 and I'd prefer to hold off on merging more changes to the current renderer. I think we should leave this open. If the renderer overhaul lands prior to 0.6 (which we're working very hard to do), we can close this out. If not, we can merge this to provide some extra value in 0.6.

[mockersf]

there is now a

bevy/crates/bevy_pbr/src/bundle.rs

Lines 70 to 78 in add1818

	/// A component bundle for [`DirectionalLight`] entities.
	#[derive(Debug, Bundle, Default)]
	pub struct DirectionalLightBundle {
	pub directional_light: DirectionalLight,
	pub frustum: Frustum,
	pub visible_entities: VisibleEntities,
	pub transform: Transform,
	pub global_transform: GlobalTransform,
	}

in main