Support for PHP8

use by `compose update`
```
Problem 1
    - ahsankhatri/wordpress-auth-provider[v2.0.0, ..., v2.x-dev] require php ^7.1 -> your php version (8.0.3) does not satisfy that requirement.
    - Root composer.json requires ahsankhatri/wordpress-auth-provider ^2.0 -> satisfiable by ahsankhatri/wordpress-auth-provider[v2.0.0, ..., v2.x-dev].
```