Replace dynamic property with passing a callback to the sort() method

[ovenum]

As mentioned on the Discord Server, the Sorting Cookbook article currently makes use of dynamic properties that will cause a deprecation warning in PHP 8.2. Support for dynamic properties is set to be removed in PHP 9.

This pull requests replaces the use of dynamic properties in the article with a callback function. I’m not quite sure if this is how the sort() method should be used and the guide would require more examples how to change sorting order.

[distantnative]

Is this ready to be reviewed?

[texnixe]

@distantnative We have a few other places where map() needs to be replaced, this is on my list.

https://github.com/getkirby/getkirby.com/issues/2229

[bastianallgeier]

@texnixe Could we maybe still start to merge this PR for this article?

[texnixe]

I have already fixed this in another PR now