chore: use codecov reporting

[stijnmoreels]

Use Codecov reporting.

[netlify[bot]]

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[codecov[bot]]

Codecov Report

:exclamation: No coverage uploaded for pull request base (main@733e0e9). Click here to learn what that means. Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #398 +/- ## ======================================= Coverage ? 89.85% ======================================= Files ? 20 Lines ? 1065 Branches ? 82 ======================================= Hits ? 957 Misses ? 79 Partials ? 29 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=arcus-azure). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=arcus-azure)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.

[stijnmoreels]

What do you think of this kind of reporting? Using Codedev, we can also create a status badge afterwards with a percentage in our README.md file. Right now, because main has never run with code coverage, it only shows the percentage of the PR.

[fgheysels]

Code coverage will be really helpful to see what code has not been tested, and if we can live with that. But I can already see we're at a very high coverage percentage :) Great job.