Replace StyleCI with PHP CS Fixer

[mspirkov]

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

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.65%. Comparing base (2abf35d) to head (7670dec).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #294   +/-   ##
=========================================
  Coverage     99.65%   99.65%           
  Complexity      699      699           
=========================================
  Files            23       23           
  Lines          2904     2912    +8     
=========================================
+ Hits           2894     2902    +8     
  Misses           10       10           

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