Add PHP 8.4 support

[cedric-anne]

Implicitly nullable parameter declarations are deprecated in PHP 8.4. The proposed change is safe and is not considered by PHP as a signature change, see https://php.watch/versions/8.4/implicitly-marking-parameter-type-nullable-deprecated

Unfortunately, this syntax is compatible only with PHP >= 7.1. I propose to raise the minimal PHP requirement to 7.1.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.99%. Comparing base (17bfc66) to head (ece85d8).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #69      +/-   ##
==========================================
+ Coverage   96.96%   96.99%   +0.03%     
==========================================
  Files          15       15              
  Lines         593      599       +6     
==========================================
+ Hits          575      581       +6     
  Misses         18       18              

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[cedric-anne]

Ping @vearutop .

The deprecation warning on PHP 8.4 is preventing us to active our CI checks on this incoming PHP version. We could still apply manually a patch, but we would prefer to help to fix it in your lib directly.