[REQUEST] Set up code coverage with SimpleCov + CodeCov

[etagwerker]

Before we start...:

• I checked the documentation and didn't find this feature
• I checked to make sure that this feature has not already been requested

Branch/Commit:

In the main branch.

Describe the feature:

As a maintainer/contributor
I would like to see code coverage metrics
And then I can decide which files need more tests

Resources:

It would be great to set up CodeCov and Simplecov for this project:

• https://app.codecov.io/gh/fastruby/pecas

I will abide by the code of conduct