Use dependabot to update dependencies

[jishnub]

Replace the compathelper action following https://discourse.julialang.org/t/psa-github-dependabot-now-supports-julia/134997

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.59%. Comparing base (bdc2cf2) to head (5e12dbc).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #239   +/-   ##
=======================================
  Coverage   89.59%   89.59%           
=======================================
  Files          11       11           
  Lines        1115     1115           
=======================================
  Hits          999      999           
  Misses        116      116           

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