Allow using Plates from php 7.4

[pine3ree]

Hello ragboyjr,

any reason for not keeping 7.4 as the minimum php version?

The code does not use any new php feature. In version 3.6 just a few compatibility issues (implicit nullables) were solved for newer php-versions. The only part with newer attributes is the ThemeTest class.

The ci tests work fine on my side https://github.com/pine3ree/plates/actions/runs/15336801684

kind regards