code: protected Content getNavLinkPackage(PackageElement pkg) {
          Content linkContent = getPackageLink(pkg, contents.packageLabel);
          Content li = HtmlTree.LI(linkContent);
          return li;
      }
docs: Get link to the "package-summary.html" page for the package passed.
  
  @param pkg Package to which link will be generated
  @return a content tree for the link