Add getOrElse pipe

[ciukstar]

I'm submitting a ... (check one with "x")

[ ] bug report => search github for a similar issue or PR before submitting
[x] feature request

Current behavior
No pipe for simple getOrElse function

Expected behavior
Equivalent to ts-option option(x).getOrElse(y).
Ex:
'a' | getOrElse : 'b' -> 'a'
1 | getOrElse : 2 -> 1
let x: any;
null | getOrElse : x -> x
undefined | getOrElse : x -> x

What is the motivation / use case for changing the behavior?
Very util function