[BUG] CI codecov step not allowing uploads

[fkiraly]

The codecov job codecov.yml in the CI is failing due to rate limits, as no token is being used.

This should be investigated and possibly fixed.

Temporarily, the step has been investigated.

[tschm]

I recommend to upload the coverage as artifact and then construct a little html page on the fly, for an example:

https://tschm.github.io/jquantstats/

The link in the README of jquantstats is very outdated!