Update CI config

[fingolfin]

To keep code coverage working, you'll have to define a CODECOV_TOKEN.
This can be done once in the peal GitHub org for all repositories
in it at once.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.58%. Comparing base (925b568) to head (8986a50).
Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #29   +/-   ##
=======================================
  Coverage   77.58%   77.58%           
=======================================
  Files          21       21           
  Lines        1878     1878           
=======================================
  Hits         1457     1457           
  Misses        421      421           

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.