Experimental exposition of Chimney derivation engine as a library to use by other libraries

[MateuszKubuszok]

See #573

TODO:

• make sure the example compiles tests

• make sure the code does not checks MiMa

• add documentation in cookbook

• explain that this library is experimental - Chimney checks with MiMa

  • chimney-macro-commons
  • public API of Chimney core module
  • integrations

  but Chimney core module's macros are not set in stone and can be modified in binary incompatible way.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 86.52%. Comparing base (273e77c) to head (ae09536).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
...himney/internal/compiletime/DerivationEngine.scala	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #574      +/-   ##
==========================================
- Coverage   86.57%   86.52%   -0.05%     
==========================================
  Files         154      155       +1     
  Lines        5995     6004       +9     
  Branches      544      543       -1     
==========================================
+ Hits         5190     5195       +5     
- Misses        805      809       +4     

Flag	Coverage Δ
	86.52% <0.00%> (?)

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