[11.x] Unless helper

[michaelnabil230]

Add unless() Helper Function

This PR introduces a new unless() helper function to provide a more expressive alternative to conditional logic in Laravel. The unless() function complements the existing when() function by handling the inverse logic, allowing developers to execute a given callback or return a value if the condition evaluates to false.

Example Usage:

$result = unless(false, 'Hello'); // returns 'Hello'
$result = unless(true, 'Hello', 'World'); // returns 'World'

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If applicable, please consider releasing your code as a package so that the community can still take advantage of your contributions!