Resolved light mode persist issue

[Tejashri-Taral]

Hey @JiyaGupta-cs , issue closes #503 I have resolved the issue to persist the light mode preference across page refreshes using localStorage. The changes ensure that the user's selected mode (dark or light) is maintained even after the page is refreshed.

Changes made are as follows :

Added functionality to check "localStorage" for the user's light mode preference upon page load and set the initial state accordingly. Updated the event listener for the toggle switch to save the light mode preference in localStorage whenever the user changes the mode. Now, Whenever user will refresh or log in the page again, The selected mode preference will be the same as chosen.

Screenshot/Video:

https://github.com/JiyaGupta-cs/ShopNex/assets/160386036/b06e2f60-2e97-4ab5-aba0-81d6bf26e0a9

Please take a look and review it. Also, please add the labels.