This patch adds a hover background for the wiki row in wiki list page,
which make its behavior more close to repo's file list page.
This patch also make the wiki-git-entry visible on the row is hovered
instead of the cel, so users won't be confused since the 'grid' is not
visible from the web page.
After the patch: (when the wiki named 'Home' is hovered)
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Close#20976Close#20975
1. Fix the bug: the TOC in footer was incorrectly rendered as main
content's TOC
2. Fix the layout: on mobile, the TOC is put above the main content,
while the sidebar is put below the main content
3. Auto collapse the TOC on mobile
ps: many styles of "wiki.css" are moved from old css files, so leave
nits to following PRs.