Trim relaxed-json dependencies

[fregante]

• Closes Replace relaxed-json with strip-json-comments #3910

As mentioned in #3910 (comment), relaxed-json has duplicate key detection so it cannot easily be replaced.

And we don't have to. The only problem with the package is that it has a lot of CLI dependencies.

Since the package has been stable/undeveloped for 5 years, I just forked it to publish an API-only version, documenting it: https://github.com/fregante/relaxed-json#readme. This was brought up to its developer 3 years ago already but no response.

This drops all of its deps:

[willdurand]

@fregante can you rebase please?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.77%. Comparing base (924db3f) to head (2f3881e).
Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5420   +/-   ##
=======================================
  Coverage   98.77%   98.77%           
=======================================
  Files          51       51           
  Lines        2855     2855           
  Branches      867      867           
=======================================
  Hits         2820     2820           
  Misses         35       35           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.