docs(unstable): document how to load animation from file

src/lib.rs

@@ -106,6 +106,39 @@
 //!   }
 //! }
 //! ```
+//!
+//! ## **(Unstable)** Load animation from file
+//!
+//! By enabling the cargo feature: `unstable-load-from-file` you can write the animation in an asset file with the extension `.animation.yml`
+//! then load with the asset-server.
+//!
+//! Here is how the animation file looks like:
+//! ```yaml
+//! # The mode can be one of: 'once', 'repeat', 'ping-pong'
+//! # or 'repeatFrom(n)' (where 'n' is the frame-index to repeat from)
+//! # The default is 'repeat'
+//! mode: ping-pong
+//! frames:
+//!   - index: 0 # index in the sprite sheet for that frame
+//!     duration: 100 # duration of the frame in milliseconds
+//!   - index: 1
+//!     duration: 100
+//!   - index: 2
+//!     duration: 120
+//! ```
+//!
+//! And how to load it with the asset server
+//! ```
+//! # use bevy::prelude::*;
+//! # use benimator::*;
+//! fn load(mut commands: Commands, asset_server: Res<AssetServer>) {
+//!
+//!     // Load animation from the asset server
+//!     let animation_handle: Handle<SpriteSheetAnimation> = asset_server.load("player_run.animation.yml");
+//!
+//!     // TODO insert the handle in an entity...
+//! }
+//! ```
 
 #[cfg(test)]
 #[macro_use]