Check codecov setup; Codecov badge on GitHub page is not working

[mperrin]

The README displayed at the main GitHub page https://github.com/spacetelescope/webbpsf has these little badges. I noticed the codecov one is not working:

The actual codecov coverage tests are running for each pull request, so I am not sure why this isn't working. It may be that the issue is that there's no code coverage tests on the master branch, just on the pull requests. Compare: https://app.codecov.io/gh/spacetelescope/webbpsf/pulls versus https://app.codecov.io/gh/spacetelescope/webbpsf

Not a high priority issue, but probably just need some relatively small config fix maybe?