_Promise chaining example_

In the ECS environment, you can't use the standard async/await

approach, which can make implementing asynchronous logic painful.

[pecs] is a plugin for the [Bevy][bevy] engine that solves this problem.

It allows you to execute the code asynchronously by chaining multiple

promises as part of [Bevy's `ecs`][ecs] environment.

Each promise takes state and the result of the previous promise as arguments,

as well as any Bevy ECS system parameter, and passes the modified

state and new promise/result to the next promise. It's easy to register custom

promises that wait for user input, events, asset loading, and so on. You can

also use [pecs] to wait for any or all of multiple promises to complete

before continuing with the rest of the code, as well as to loop asynchronously

until a condition is met.

[pecs]: https://github.com/jkb0o/pecs

[ecs]: https://bevyengine.org/learn/book/getting-started/ecs