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 100.00%. Comparing base (5d18903) to head (70fdb79).
⚠️ Report is 30 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff             @@
##              master       #82   +/-   ##
===========================================
  Coverage     100.00%   100.00%           
- Complexity        47        72   +25     
===========================================
  Files              8        10    +2     
  Lines            128       196   +68     
===========================================
+ Hits             128       196   +68     

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