docs: readme: update babashka badge target

[lread]

New target describes babashka badges

See babashka/babashka#1798

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.00%. Comparing base (a37f062) to head (b6aedc1).
Report is 6 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #42   +/-   ##
=======================================
  Coverage   89.00%   89.00%           
=======================================
  Files          13       13           
  Lines        1019     1019           
  Branches       48       48           
=======================================
  Hits          907      907           
  Misses         64       64           
  Partials       48       48           

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[athos]

Thanks!