This commit standardizes font sizes across components for a uniform
look. The icon sizes, font weights and line heights are also adjusted
accordingly for better standardization and simplicity.
- Introduce variables for standard font sizes, enhancing
maintainability.
- Remove explicit pixel values, replaced with scalable units based on
root size.
- Remove workaround for line-height adoptation of bigger font-size.
- Use consistent small font-size for the code area.
- Adjust checkbox tick to scale with font size.