New CSS custom properties

[Giildo]

Is your feature request related to a problem? Please describe.

To create documentation at our university, I’d like to use Vitepress. To customize the documentation, I want to use elements from our design system, including our font.
The problem is that our font is very small compared to others. So I have to increase all the font-size values by 25% to keep it readable.

Describe the solution you'd like

Two complementary solutions:

1. Use only rem values so that I can increase the font-size of html to proportionally increase all font sizes.
2. Use custom properties to fine-tune the values without affecting the overall style.

Additional context

Adjust the line-height values so that they comply with WCAG Criterion 1.4.12 by setting them to at least 1.5 times the font height (remove the value if it is less than or equal to 1.5 to use the default value).

Validations

• Follow our Code of Conduct
• Read the docs.
• Read the Contributing Guidelines.
• Check that there isn't already an issue that asks for the same feature to avoid creating a duplicate.