Allow concatmap, flatmap and switchmap to receive an async function

[vxgmichel]

Fix #129
Obsolete #140

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (157ae89) to head (7b94d85).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #143   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           15        15           
  Lines         1160      1172   +12     
=========================================
+ Hits          1160      1172   +12     

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