Add support for PHPUnit 12

[TomaszGasior]

Currently it's impossible to install Pip in PHPUnit 12. PHPUnit 12 has been released in February 2025.

[Bilge]

Can you PR that?

[rdotter]

@Bilge added #22 as change for allowing PHPunit 12

[ireneperezddc1]

I suggest this: #23

[Bilge]

Complete via #23. Thank you @ireneperezddc1.