chore: replace nyc with c8 for coverage reporting in `package.jso…

…n` (#149)

This pull request includes changes to the `package.json` file to update
the code coverage tool from `nyc` to `c8`.

Changes to code coverage tool:

* Replaced `nyc` with `c8` in the `coverage` script.
* Added `c8` as a new dependency.
* Removed `nyc` from the list of dependencies.