Rework the async startegy

[Baptouuuu]

Fix #31

Unlike mentioned in the issue the asAsync method as been added to the Config class instead of the Transport one in order to not duplicate the transformation logic.

[codecov]

Codecov Report

❌ Patch coverage is 28.37838% with 53 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.78%. Comparing base (496fa78) to head (7ddc22a).

Files with missing lines	Patch %	Lines
src/Config.php	27.77%	13 Missing ⚠️
src/Transport/CircuitBreaker.php	0.00%	9 Missing ⚠️
src/Transport/ExponentialBackoff.php	0.00%	9 Missing ⚠️
src/Config/Async.php	0.00%	7 Missing ⚠️
src/Transport/Via.php	14.28%	6 Missing ⚠️
src/Transport/Curl.php	83.33%	3 Missing ⚠️
src/Transport/FollowRedirections.php	0.00%	3 Missing ⚠️
src/Transport/Logger.php	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main      #36      +/-   ##
============================================
- Coverage     91.90%   89.78%   -2.13%     
- Complexity      371      390      +19     
============================================
  Files            30       31       +1     
  Lines          2039     2104      +65     
============================================
+ Hits           1874     1889      +15     
- Misses          165      215      +50     

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