Add a link for Package Versions usage documentation

src/Packagist/WebBundle/Resources/views/Web/index.html.twig

@@ -15,6 +15,8 @@
     }
 }</code></pre>
 
+            <p>For more information about packages versions usage, see the <a href="https://getcomposer.org/doc/01-basic-usage.md#package-versions">composer documentation</a>.</p>
+
             <h3>Install Composer In Your Project</h3>
             <p>Run this in your command line:</p>
             <pre><code>curl -sS https://getcomposer.org/installer | php</code></pre>