🔴 Title :Add dark mode theme in story builder

🔴 Enhancement Aim :User can choose theme according to their interest
🔴 Changes : use HTML,CSS,Javascript

Screenshots 📷

✅ Details to Include When Taking the Issue:
Name :Mansi
Participant Role (Specify the Open Source Program name, e.g., GSSOC, Hacktoberfest, etc.):
GSSOC-Ext

Happy Contributing! 🚀

Wishing you all the best on your open source journey. Enjoy! 😎