Add About Us page

## Description

The website does not currently have an About Us page, which is important for introducing the organization, its mission, values, and team. Without this, users cannot learn about the purpose and background of the platform.

## Expected Behaviour

A new about.html page should be created.

The page should include:

- Organization/website history
- Mission and vision statements
- Key achievements
- Timeline or milestones (optional)
- A link to the About Us page should be added in the header navigation and footer.

## Suggested Enhancements

- Use a clean and engaging design with images/icons.
- Add scroll/hover effects for interactivity.
- Ensure it supports Dark Mode.
- Make the layout responsive for all screen sizes.