[Feature] Integrate Dark Mode to Website

## Problem ❓
As a user, I would like to add a feature to toggle the `dark mode` on the website for better visibility and to reduce eye strain.

## Features to add✨

- Dark mode toggle switch in the site's *header* or *footer*.
- Customize color options for the *dark mode* to suit user preferences.
- Ability to remember the user's dark mode preference across sessions.
- Improve site's accessibility by adding screen reader support. (Optional)
- Implement a fully furnished responsive design to improve the site's mobile usability. (current one includes padding, margin & overflow issues in responsive mode, with inconsistent font-size in general.)

This issue will help to enhance the website's functionality and user experience and make it more accessible and user-friendly for everyone.

## Implementation

- [x] I would be interested in implementing this feature.

cc: @TimidRobot, @brylie, @possumbilities