Add documentation to Bundle macro

Signed-off-by: Marcel Müller <[email protected]>

Author: TheNeikos

crates/bevy_ecs/src/bundle.rs

@@ -2,6 +2,54 @@
 //!
 //! This module contains the [`Bundle`] trait and some other helper types.
 
+/// Derive the [`Bundle`] trait
+///
+/// You can apply this derive macro to structs that are
+/// composed of [`Component`]s or
+/// other [`Bundle`]s.
+///
+/// ## Attributes
+///
+/// Sometimes parts of the Bundle should not be inserted.
+/// Those can be marked with `#[bundle(ignore)]`, and they will be skipped.
+/// In that case, the field needs to implement [`Default`] unless you also ignore
+/// the [`BundleFromComponents`] implementation.
+///
+/// ```rust
+/// # use bevy_ecs::prelude::{Component, Bundle};
+/// # #[derive(Component)]
+/// # struct Hitpoint;
+/// #
+/// #[derive(Bundle)]
+/// struct HitpointMarker {
+///     hitpoints: Hitpoint,
+///
+///     #[bundle(ignore)]
+///     creator: Option<String>
+/// }
+/// ```
+///
+/// Some fields may be bundles that do not implement
+/// [`BundleFromComponents`]. In those cases you can either ignore it as above,
+/// or you can opt out the whole Struct by marking it as ignored with
+/// `#[bundle(ignore_from_components)]`.
+///
+/// ```rust
+/// # use bevy_ecs::prelude::{Component, Bundle, ChildOf, Spawn};
+/// # #[derive(Component)]
+/// # struct Hitpoint;
+/// # #[derive(Component)]
+/// # struct Marker;
+/// #
+/// use bevy_ecs::spawn::SpawnRelatedBundle;
+///
+/// #[derive(Bundle)]
+/// #[bundle(ignore_from_components)]
+/// struct HitpointMarker {
+///     hitpoints: Hitpoint,
+///     related_spawner: SpawnRelatedBundle<ChildOf, Spawn<Marker>>,
+/// }
+/// ```
 pub use bevy_ecs_macros::Bundle;
 
 use crate::{