Add CodeCov token.

Author: tillig

.github/workflows/build.yml

@@ -24,4 +24,5 @@ jobs:
       with:
         fail_ci_if_error: true
         files: artifacts/logs/*/coverage.cobertura.xml
+        token: ${{ secrets.CODECOV_TOKEN }}
 # TODO: Upload to GitHub packages instead of MyGet in GitHub actions for master and develop.