code: public Builder text(String s) {
          // null values add no text
          if (s == null) {
              return this;
          }
          html.a(Util.escapeXml(s));
          text.a(s);
          return this;
      }
docs: Adds text to both the HTML and the plain text version. The HTML version
  is escaped of all XML tags.
  
  @param s the text to append
  @return this builder