fix: navLi active text colour (dark)

## 📑 Description Change text colour of active navLi to white when in dark mode: Before:  After:  <!-- You can also choose to add a list of changes and if they have been completed or not by using the markdown to-do list syntax - [ ] Not Completed - [x] Completed --> ## ✅ Checks <!-- Make sure your pr passes the tests and do check the following fields as needed - --> - [x] My pull request adheres to the code style of this project - [ ] My code requires changes to the documentation - [x] I have updated the documentation as required - [x] All the tests have passed ## ℹ Additional Information