Replace StyleCI with PHP CS Fixer

[mspirkov]

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

[codecov]

Codecov Report

❌ Patch coverage is 76.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.29%. Comparing base (d2ca052) to head (07bef51).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/ErrorHandler.php	25.00%	3 Missing ⚠️
src/Exception/ErrorException.php	0.00%	1 Missing ⚠️
src/HeadersProvider.php	50.00%	1 Missing ⚠️
src/Renderer/HtmlRenderer.php	87.50%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #163      +/-   ##
============================================
+ Coverage     78.99%   79.29%   +0.30%     
  Complexity      197      197              
============================================
  Files            19       19              
  Lines           619      628       +9     
============================================
+ Hits            489      498       +9     
  Misses          130      130              

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