* feat(lint): add php-cs-fixer for linting
Removing previous CODE_STYLE as it was not enforced anyway and using PER-CS 2.0.
This is not the reformatting commit.
* style: format code according to PER-CS 2.0 with php-cs-fixer
* ci(actions): add lint action
Resolves#1132.
Native strftime was deprecated in PHP 8.1 so I replaced it with an
alternative library that uses ICU so that you don't have to set up
locales on your server anymore.
Also this commit removes AM/PM labels as timestamps were in 24h format
anyways, regardless of locale.
