Enhancement: Add Config\Ruleset\Php84 rule set

[localheinz]

This pull request

• adds a Config\Ruleset\Php84 rule set

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (c2ea1ce) to head (ca03e81).
Report is 2 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##                main     #1140    +/-   ##
============================================
  Coverage     100.00%   100.00%            
- Complexity        70        71     +1     
============================================
  Files             22        23     +1     
  Lines          11419     12303   +884     
============================================
+ Hits           11419     12303   +884     

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