title: Should I assume that ^[a-z]{2} will match any locale?
body: <p>I'm implementing the routing and i18n part of my framework. I'm wondering if I should assume that </p>
  
  <pre><code>^[a-z]{2} 
  </code></pre>
  
  <p>Will be a locale, and if so use it. Or should I make the user populate a list with languages? Eg:</p>
  
  <pre><code>supported = [ 'en', 'es', 'it', 'ru', ]
  </code></pre>
  
  <p>So the developer has to manually define languages. And for the record, 90% of the sites here only use <code>en</code> only.</p>