code: public S intersperse(T delimiter) {
          return supply(stream().flatMap(s -> StreamEx.of(delimiter, s)).skip(1));
      }
docs: Returns a new stream containing all the elements of the original stream interspersed with
  given delimiter.
  
  <p>
  For example, {@code StreamEx.of("a", "b", "c").intersperse("x")} will yield a stream containing
  five elements: a, x, b, x, c.
  
  <p>
  This is an <a href="package-summary.html#StreamOps">intermediate operation</a>.
  
  @param delimiter a delimiter to be inserted between each pair of elements
  @return the new stream
  @since 0.6.6