chore(package): update fetch-mock to version 5.12.0

[citizensas]

Closes #87

[codecov]

Codecov Report

Merging #88 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #88   +/-   ##
=======================================
  Coverage   73.64%   73.64%           
=======================================
  Files           1        1           
  Lines         148      148           
  Branches       30       30           
=======================================
  Hits          109      109           
  Misses         27       27           
  Partials       12       12

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