Add token to codecov upload

[anissa111]

PR Summary

Closes #565

So, I'm not entirely sure how to test this because the failures only come from main on the NCAR/geocat-comp repo.

I followed this documentation from Codevoc: Adding the Codecov Token

PR Checklist

General

• Make an issue if one doesn't already exist
• Link the issue this PR resolves by adding closes #XXX to the PR description where XXX is the number of the issue.
• Add a brief summary of changes to docs/release-notes.rst in a relevant section for the next unreleased release. Possible sections include: Documentation, New Features, Bug Fixes, Internal Changes, Breaking Changes/Deprecated
• Add appropriate labels to this PR
• Make your changes in a forked repository rather than directly in this repo
• Open this PR as a draft if it is not ready for review
• Convert this PR from a draft to a full PR before requesting reviewers
• Passes precommit. To set up on your local, run pre-commit install from the top level of the repository. To manually run pre-commits, use pre-commit run --all-files and re-add any changed files before committing again and pushing.
• If needed, squash and merge PR commits into a single commit to clean up commit history

[anissa111]

It worked 🎉 https://app.codecov.io/gh/NCAR/geocat-comp/commits