title: How do can I add a new format option to Moment.js locales?
body: <p>I want to be able to format a date as the day and the shortened month. (ex: 20 Sep for en-gb, Sep 20 for en). However, the closest localized format that Moment.js has us the format 'll' which is Sep 20, 2017 for en. I want to be able to create a new format that excludes the year from 'll'. How can I best achieve this?</p>
  
  <p>The end result I want (assuming today is Sept 20): </p>
  
  <pre><code>moment.locale('en');
  moment().format('my-new-format')  ---&gt; Sep 20
  moment.locale('en-gb');
  moment().format('my-new-format')  ---&gt; 20 Sep
  moment().format('ll')             ---&gt; 20 Sep, 2017
  </code></pre>