Drop support for Julia 1.5 and earlier (and bump the version from 1.1.0 to 1.2.0)

[DilumAluthge]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.36%. Comparing base (a5d058d) to head (be317b7).

Additional details and impacted files

@@                  Coverage Diff                  @@
##           DilumAluthge-patch-1      #73   +/-   ##
=====================================================
  Coverage                 89.36%   89.36%           
=====================================================
  Files                         2        2           
  Lines                        94       94           
=====================================================
  Hits                         84       84           
  Misses                       10       10           

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