title: List of all the geographic scope in Plotly
body: <p>I am trying to plot data on a map using <code>plotly.js</code>. I know that you can achieve a map of a country from:</p>
  
  <pre><code>layout = dict(
          title = '',
          geo = dict(
              scope='usa',
              ...
               )
  </code></pre>
  
  <p>Do we have a list of available scopes, i.e. different regions, some where? I have tried googling it but can't seem to find it. In the example they have 'africa' as well, but how about other places?</p>