<p>Called when determining which extra icons are currently in use. These icons will be included in the generated sprites.</p>

<p><strong>This is a simple event for adding a static set of icons. For more advanced cases, extend <code>\XF\Service\Icon\UsageAnalyzerService</code> instead.</strong></p>

<p>Callback signature:</p>
<blockquote><code><em>array</em> &amp;$icons</code></blockquote>

<p>Arguments:</p>
<ol>
	<li><code><em>array</em> &amp;$icons</code> - An array of strings containing icon classes, for example 'fas fa-acorn'.</li>
</ol>