add simple doc strings for GpuAtmosphere and ExtractedAtmosphere

Author: ecoskey

crates/bevy_pbr/src/atmosphere/mod.rs

@@ -268,6 +268,8 @@ impl ExtractComponent for Atmosphere {
     }
 }
 
+/// The render-world representation of an `Atmosphere`, but which
+/// hasn't been converted into shader uniforms yet.
 #[derive(Clone, Component)]
 pub struct ExtractedAtmosphere {
     pub bottom_radius: f32,

crates/bevy_pbr/src/atmosphere/resources.rs

@@ -520,8 +520,10 @@ pub(super) fn prepare_atmosphere_textures(
 #[error("ScatteringMedium missing with id {0:?}: make sure the asset was not removed.")]
 struct ScatteringMediumMissingError(AssetId<ScatteringMedium>);
 
+/// The shader-uniform representation of an Atmosphere.
 #[derive(Clone, Component, ShaderType)]
 pub struct GpuAtmosphere {
+    //TODO: rename to Planet later?
     pub ground_albedo: Vec3,
     pub bottom_radius: f32,
     pub top_radius: f32,