Enhancement: Add phpstan-extreme-rules as keyword

[localheinz]

This PR

• adds phpstan-extreme-rules as keyword to composer.json

[codecov]

Codecov Report

Merging #27 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             master    #27   +/-   ##
=======================================
  Coverage       100%   100%           
  Complexity       21     21           
=======================================
  Files             4      4           
  Lines            50     50           
=======================================
  Hits             50     50

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