code: public Content getNavLinkNext() {
          Content li;
          if (next == null) {
              li = HtmlTree.LI(nextpackageLabel);
          } else {
              DocPath path = DocPath.relativePath(packageDoc, next);
              li = HtmlTree.LI(getHyperLink(path.resolve(DocPaths.profilePackageSummary(profileName)),
                  nextpackageLabel, "", ""));
          }
          return li;
      }
docs: Get "NEXT PACKAGE" link in the navigation bar.
  
  @return a content tree for the next link