chore: make type fest a non-dev dependency

[alexbarnsley]

Summary

Adding utils as a dependency resulted in an error with not being able to find the type-fest dependency.

Checklist

• Documentation (if necessary)
• Tests (if necessary)
• Ready to be merged

[codecov]

Codecov Report

Merging #65 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #65   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files         193    193           
  Lines        1172   1172           
  Branches      113    113           
=====================================
  Hits         1172   1172

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