fix(markup): resolve and proxy srcset links of <source> elements (#39708)

1. use correct links for srcset attribute of picture source
2. wrap the picture element with a link correctly

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

modules/markup/render_link.go

@@ -42,7 +42,7 @@ func resolveLinkRelative(ctx context.Context, base, cur, link string, absolute b
 			finalLink += "?" + linkURL.RawQuery
 		}
 		if linkURL.Fragment != "" {
-			finalLink += "#" + linkURL.Fragment
+			finalLink += "#" + linkURL.EscapedFragment()
 		}
 	}