code: public static HtmlTree LINK(String rel, String type, String href, String title) {
          HtmlTree htmltree = new HtmlTree(HtmlTag.LINK);
          htmltree.addAttr(HtmlAttr.REL, nullCheck(rel));
          htmltree.addAttr(HtmlAttr.TYPE, nullCheck(type));
          htmltree.addAttr(HtmlAttr.HREF, nullCheck(href));
          htmltree.addAttr(HtmlAttr.TITLE, nullCheck(title));
          return htmltree;
      }
docs: Generates a LINK tag with the rel, type, href and title attributes.
  
  @param rel relevance of the link
  @param type type of link
  @param href the path for the link
  @param title title for the link
  @return an HtmlTree object for the LINK tag