Refactor CSS to use more Variables

[jineshnagori]

The CSS files (style.css and darktheme.css) could be more maintainable. Refactor the CSS to make better use of variables for colors, fonts, and spacing.

[vanshikasoni22]

Hi @jineshnagori Can you assign this issue to me

[abhinavsingh-hub]

Greetings @jineshnagori ! I would love to work on this, can you assign this issue to me?