feat: CICD: Code Coverage Badges

[ProgrammingByPermutation]

There are a couple of solutions in how to implement a badge to show how much code coverage the application has in the README.

Ideally, I would prefer not to integrate a 3rd party solution but see what the options are.

[ProgrammingByPermutation]

Codecov is free for opensource projects:
https://about.codecov.io/pricing/