Next/prev link detection improvements

[1j01]

• Hidden links should be de-prioritized / excluded
• Prioritize links in navigation
  • nav, .paginate, .pagination, .pages, .nav, .navigation e.g. (but much looser)
  • Prioritize links nearby in hierarchy to a paired next/prev link (could be an unreliable factor if links are hidden at the first / last page)
• Penalize links in a comments section
  • .comments, .comment_area, .responses e.g.
• Should keyboard shortcuts (left/right) be a separate browser extension?
• Automated tests

Note: webtoons uses .paginate for both the main nav and pagination of the comments area.