lib/game/observable-arrays.js
function startWatchingarray(ko, observable, array) {
  var subscribable = getSubscribableForArray(ko, array);
  return subscribable.subscribe(observable);
}
function startWatchingarray(ko, observable, array) {
  var subscribable = getSubscribableForArray(ko, array);
  return subscribable.subscribe(observable);
}
Listens for array mutations, and when they happen, cause the observable to fire notifications. This is used to make model properties of type array fire notifications when the array changes. Returns a subscribable that can later be disposed.