chore: add codecov

Author: mvexel

.github/workflows/ci.yml

@@ -37,3 +37,11 @@ jobs:
 
       - name: Run tests with tox
         run: poetry run tox
+
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@v4.0.1
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
+          # files: ./coverage.xml # Adjust this path if necessary
+          # flags: unittests # Optional flags for Codecov
+          # fail_ci_if_error: true # Fails the CI if Codecov upload fails