title: Append value to List
body: <p>I have a immutable list object, within a <code>Map</code> object, as follows:</p>
  
  <pre><code>let initialState = Immutable.fromJS({});
  state = initialState;
  state = state.set("myList", Immutable.List());
  </code></pre>
  
  <p>How do I append a value to "myList", thereby updating <code>state</code>?</p>