title: How to set default value in BehaviourSubject
body: <p>Probably a noob question. How do I set a default value to a BehaviourSubject.</p>
  
  <p>I have an enum with 2 different values</p>
  
  <pre><code>enum class WidgetState {
      HIDDEN,
      VISIBLE
  }
  </code></pre>
  
  <p>And a behaviour subject which emits the states</p>
  
  <pre><code>val widgetStateEmitter: BehaviorSubject&lt;WidgetState&gt; = BehaviorSubject.create()
  </code></pre>
  
  <p>My emitter starts emitting when the view logic is written. However it's HIDDEN by default. How do I set the default value as WidgetState.HIDDEN to my emitter <code>widgetStateEmitter</code>?</p>