fix: covariance possible issues

[belgattitude]

• Update Q&A (psalm/phpstan)
• ProcessExceptionInterface: prevent covariance issues
• NullCache: fixed minor issue with latest phpstan:

 ------ -------------------------------------------------------------------- 
  Line   src/Common/Cache/NullCache.php                                      
 ------ -------------------------------------------------------------------- 
  40     Return type (mixed) of method                                       
         Soluble\MediaTools\Common\Cache\NullCache::getMultiple() should be  
         covariant with return type (iterable) of method                     
         Psr\SimpleCache\CacheInterface::getMultiple()                       
 ------ -------------------------------------------------------------------- 

• Added changelog entries

[codecov]

Codecov Report

Merging #21 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master      #21   +/-   ##
=========================================
  Coverage     98.06%   98.06%           
  Complexity      680      680           
=========================================
  Files            51       51           
  Lines          1448     1448           
=========================================
  Hits           1420     1420           
  Misses           28       28           

Impacted Files	Coverage Δ	Complexity Δ
src/Common/Cache/NullCache.php	100.00% <ø> (ø)	9.00 <0.00> (ø)

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