title: How can I get a list of all categories in GetEventStore?
body: <p>From streams like these:</p>
  
  <ul>
  <li>sales-sale102</li>
  <li>sales-sale103</li>
  <li>sales-sale104</li>
  <li>users-8989</li>
  <li>users-8990</li>
  </ul>
  
  <p>Get somethig like this:</p>
  
  <pre><code>[ "sales", "users"]
  </code></pre>