Proposal to add yielder.prepend

[JosephTLyons]

I'm proposing there be a prepend function in yielder. The yielder API seems to closely match the list API. list has prepend. Additionally, yielder has yield, which does a prepend, but is a bit awkward to use in pipes. A prepend method would be convenient and as simple as:

pub fn prepend(yielder: Yielder(a), element: a) -> Yielder(a) {
  use <- yielder.yield(element)
  yielder
}

[lpil]

Sounds fab to me!