docs(readme): Document how the project compare to bevy_rapier

Resolve jcornaz#112

README.md

@@ -98,6 +98,23 @@ One must choose to use either `2d` or `3d` (but not both). If none of theses two
 * `debug-2d` Render 2d collision shapes. Works only in 2d, support for 3d may be added later.
 
 
+## How does this project compare to bevy_rapier?
+
+[bevy_rapier] plugin is an excellent option and should definitely be considered.
+
+Here are some key differences between the two projects:
+
+* `heron` tries to provide a smaller, simpler API that is easier to use. `bevy_rapier` is more complete and powerful, but a bit more complex.
+* `heron` mostly hides the underlying physics engine, so you don't have to use [rapier] directly nor [nalgebra]. `bevy_rapier` asks the user to deal directly with `rapier` and `nalgebra`.
+* `heron` is focused on games only. `bevy_rapier` targets all kind of physics simulation applications (incl. games).
+* `bevy_rapier` is actively maintained by [dimforge], the developer of `rapier`. `heron` is also active, but cannot evolve as fast as `bevy_rapier` can. 
+
+
+`heron` is probably more suited for simple games and game-jams, where the ease of learn/use is especially valuable and where the lack of advanced feature isn't problematic.
+
+`bevy_rapier` is probably more suited for bigger/complex games and other types of physics simulations, where it may be better to learn/use a more exhaustive/complex API. 
+
+
 ## Contribute / Contact
 
 You can open issues/discussions here or you can discuss with me (`Jomag#2675`) in the [bevy discord](https://discord.com/invite/gMUk5Ph)
@@ -107,3 +124,6 @@ See [how to contribute](https://github.com/jcornaz/heron/blob/main/CONTRIBUTING.
 
 [bevy]: https://bevyengine.org
 [rapier]: https://rapier.rs
+[bevy_rapier]: https://github.com/dimforge/bevy_rapier
+[dimforge]: https://www.dimforge.com
+[nalgebra]: https://github.com/dimforge/nalgebra