code: func (f *Fpdf) LinkString(x, y, w, h float64, linkStr string) {
  	f.newLink(x, y, w, h, 0, linkStr)
  }
docs: // LinkString puts a link on a rectangular area of the page. Text or image
  // links are generally put via Cell(), Write() or Image(), but this method can
  // be useful for instance to define a clickable area inside an image. linkStr
  // is the target URL.