Inline styles within side navigation bars prevents overriding

[Chng-Zhi-Xuan]

• MarkBind Version: v1.19.2

Issue

Currently site-nav and page-nav uses inline styles to format its list items.

This prevents the author from overriding the style.

Desired outcome

Shift the inline styles to a class within site-nav.css and page-nav.css, which allows overriding.