fix: enable related articles widget on article pages
The related widget was not displaying because the condition used .Type (the article's frontmatter type field like "life", "tech") instead of .Section (the content section like "articles"). Changed condition from eq .Type "articles" to eq .Section "articles".
Also added Hugo's [related] configuration block to enable content matching by categories (weight 100) and tags (weight 80) with an 80% threshold for finding related posts.
