Use json formatter to report coverage

[Earlopain]

Its buildin (or rather a default dependency on simplecov) and as such doesn't require an extra dependecy. Codecov just handles this format.

---

There are also some other things I want to bring attention to that don't directly relate this this repo: https://about.codecov.io/language/ruby/

• Ruby Standard 1 is archived
• Ruby Standard 2 says its using the bash uploader which I don't think is a thing anymore (or rather deprecated). I don't think it should be listed there either.
• Ruby Uploader repo is archived

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.90%. Comparing base (d3fe9f6) to head (6438897).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #21   +/-   ##
=======================================
  Coverage   90.90%   90.90%           
=======================================
  Files           1        1           
  Lines          11       11           
=======================================
  Hits           10       10           
  Misses          1        1           

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

[thomasrockhu-codecov]

@Earlopain thanks for this!