Add CODECOV_TOKEN

Till now it was optional but soon it will become mandatory so,
better, we add it already.

The token value can be looked (or updated) from codecov.io.

Author: stronk7

.github/workflows/test.yml

@@ -51,6 +51,7 @@ jobs:
     - name: Upload coverage
       uses: codecov/codecov-action@v3
       with:
+        token: ${{ secrets.CODECOV_TOKEN }}
         files: ./build/logs/clover.xml
         verbose: true