fix: tweak border color

Author: egoist

src/utils/cssVariables.js

@@ -19,8 +19,7 @@ const defaultCssVariables = {
   warningColor: '#ff9800',
   dangerColor: 'rgb(255, 0, 31)',
   navLinkColor: '#2c3e50',
-  navLinkBorderColor: '#fff',
-  navLinkHoverBorderColor: '#e2e2e2',
+  navLinkBorderColor: 'var(--accent-color)',
   codeBlockBackground: '#011627',
   codeBlockTextColor: 'white',
   codeBlockShadowColor: '#333',