Raise minimum PHP version up to 8.1

[Tigrov]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	✔️/❌

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.71%. Comparing base (e9805e2) to head (2e548b9).
Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #272      +/-   ##
============================================
- Coverage     99.90%   99.71%   -0.19%     
  Complexity      315      315              
============================================
  Files            21       21              
  Lines          1056     1056              
============================================
- Hits           1055     1053       -2     
- Misses            1        3       +2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.