Styling improvements & basic code refractoring

[Marigameo]

Describe the bug Few basic style improvements & code refactoring can be done as follows

• Outline looks awkward in input & select because of the gradient shade - guess that can be removed
• style.css can be refactored - existing variables can be used for colors and lines can be reduced by clubbing common styles
• Prev, next button looks rounded, can be reduced just like above select

To Reproduce https://ankitsaxena21.github.io/Food-Ordering-App/

Expected behavior

Screenshots