feat: add spawn option to entities creation

[Tochemey]

closes #117

[codecov]

Codecov Report

Attention: Patch coverage is 78.94737% with 8 lines in your changes missing coverage. Please review.

Project coverage is 85.91%. Comparing base (bcc2c66) to head (c1326ea).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
engine.go	80.00%	4 Missing and 1 partial ⚠️
spawn_config.go	75.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #121      +/-   ##
==========================================
+ Coverage   85.19%   85.91%   +0.71%     
==========================================
  Files          16       17       +1     
  Lines        1108     1136      +28     
==========================================
+ Hits          944      976      +32     
+ Misses        125      122       -3     
+ Partials       39       38       -1     

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