Replace StyleCI with PHP CS Fixer

[mspirkov]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Fixed issues	comma-separated list of tickets # fixed by the PR, if any

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.66%. Comparing base (13bba5f) to head (8871bf1).
⚠️ Report is 18 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #106   +/-   ##
=========================================
  Coverage     99.66%   99.66%           
- Complexity      108      109    +1     
=========================================
  Files            13       13           
  Lines           298      302    +4     
=========================================
+ Hits            297      301    +4     
  Misses            1        1           

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