CI: add codecov step

Author: lucascolley

.github/workflows/ci.yml

@@ -63,7 +63,7 @@ jobs:
       - name: Test package
         run: pixi run -e ${{ matrix.environment }} test-ci
 
-      # - name: Upload coverage report
-      #   uses: codecov/codecov-action@v4.5.0
-      #   with:
-      #     token: ${{ secrets.CODECOV_TOKEN }}
+      - name: Upload coverage report
+        uses: codecov/codecov-action@v4.5.0
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}