Attempt to fix codecov upload.

Author: dlongley

.github/workflows/main.yml

@@ -67,7 +67,8 @@ jobs:
     - name: Generate coverage report
       run: npm run coverage-ci
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v3
+      uses: codecov/codecov-action@v4
       with:
         file: ./coverage/lcov.info
         fail_ci_if_error: true
+        token: ${{ secrets.CODECOV_TOKEN }}