Update documentation & test matrix

[luispabon]

Changes:

• Update method jsdocs with actual contents of the method signatures
• rename callback to retryCallback
• Update README with function signature docs
• Remove license from README and point to LICENSE file
• Update copyright year on LICENSE
• Remove old concourse pipeline files
• Tweak github test matrix to test on node 16, 18 and 20

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.90%. Comparing base (bbcaf8c) to head (f4608eb).
Report is 32 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #11   +/-   ##
=======================================
  Coverage   84.90%   84.90%           
=======================================
  Files           1        1           
  Lines          53       53           
=======================================
  Hits           45       45           
  Misses          8        8           

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