[9.x] Add ability to push additional pipes onto a pipeline via chain($pipes)

[stevebauman]

Description

This PR adds the ability to push additional pipes onto a pipeline via a chain() method.

This allows us to create a pipeline instance and pass it around the application, appending pipes onto the chain, rather than having to define all of the pipes in a single place:

$pipeline = new Pipeline();

$pipeline->chain(fn ($object, $next) => $next($object));
$pipeline->chain(fn ($object, $next) => $next($object));

$pipeline->send($object)->thenReturn();

Let me know if you would like anything adjusted. Thanks for your time! ❤️

[taylorotwell]

Any thoughts on naming this method pipe instead of chain?

[stevebauman]

Yea, I'm cool with that name 👍