fix(theme): dropdown menu partially hidden by the homepage footer when it is too long

[zonemeen]

fix #2900

And I remove an unused css variable --vp-z-index-layout-top.

[brc-dd]

Ah, --vp-z-index-layout-top is meant for custom banners. It isn't documented yet (#2071). Refer this: https://github.com/faker-js/faker/blob/next/docs/.vitepress/components/Banner.vue#L83.

The order should be this IMO:

  --vp-z-index-footer: 10;
  --vp-z-index-local-nav: 20;
  --vp-z-index-nav: 30;
  --vp-z-index-layout-top: 40;
  --vp-z-index-backdrop: 50;
  --vp-z-index-sidebar: 60;

[zonemeen]

Ah, --vp-z-index-layout-top is meant for custom banners. It isn't documented yet (#2071). Refer this: https://github.com/faker-js/faker/blob/next/docs/.vitepress/components/Banner.vue#L83.

Ah, I didn't notice that. I'll reorder these css variables.