title: Font awesome icons are not displayed when exporting HTML to PDF with Dompdf
body: <p>I am using Dompdf to export an HTML page to PDF. I am using some Font Awesome icons that are displayed in the HTML file itself, but in the resulting PDF, there are question marks instead of icons.</p>
  
  <p>Here is part of the HTML code:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html lang="es"&gt;
  
  &lt;head&gt;
      &lt;meta charset="utf-8"/&gt;
  &lt;meta http-equiv="X-UA-Compatible" content="IE=edge"&gt;
  &lt;meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1" /&gt;
  &lt;title&gt;Some title&lt;/title&gt;
      &lt;!-- Latest compiled and minified CSS - Bootstrap--&gt;
  &lt;link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.5/css/bootstrap.min.css"&gt;        
  &lt;link href="http://domain.com/public/assets/css/font-awesome-4.6.0/css/font-awesome.min.css" rel="stylesheet"&gt;
  
  &lt;/head&gt;
  &lt;body&gt;
  &lt;!-- --&gt;
  
  &lt;div id="wrapper" &gt;        &lt;div id="page-wrapper"&gt;        &lt;div class="container-fluid"&gt;
              &lt;div class="row"&gt;
                  &lt;div class="col-xs-10 col-xs-offset-1"&gt;
                      &lt;div class="panel panel-default panel-table"&gt;
                          &lt;div class="panel-heading"&gt;
      &lt;div class="row"&gt;
          &lt;div class="col-xs-12"&gt;
              &lt;div class="bs-callout bs-callout-primary"&gt;
                  &lt;h4&gt;Contact name&lt;/h4&gt;
                  &lt;ul&gt;
                      &lt;li&gt;&lt;span class="fa fa-envelope"&gt;&lt;/span&gt; &lt;strong&gt;Email&lt;/strong&gt;: some@mail.com&lt;/li&gt;
                      &lt;li&gt;&lt;span class="fa fa-phone"&gt;&lt;/span&gt; &lt;strong&gt;Telephone&lt;/strong&gt;: 0000-0000&lt;/li&gt;
                      &lt;li&gt;&lt;span class="fa fa-location-arrow"&gt;&lt;/span&gt; &lt;strong&gt;Location&lt;/strong&gt;: Address&lt;/li&gt;
                  &lt;/ul&gt;
              &lt;/div&gt;
          &lt;/div&gt;
              &lt;/div&gt;
  &lt;/div&gt;
  &lt;div class="panel-body"&gt;
  
  &lt;!-- A table goes here --&gt;
  
  
      &lt;/div&gt;                                                                                                &lt;/div&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          &lt;/div&gt;
      &lt;/div&gt;
  &lt;/div&gt;&lt;!-- .wrapper --&gt;
  
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>Those icons are not displayed, only questions marks instead in the PDF:</p>
  
  <pre><code>&lt;li&gt;&lt;span class="fa fa-envelope"&gt;&lt;/span&gt; &lt;strong&gt;Email&lt;/strong&gt;: some@mail.com&lt;/li&gt;
                      &lt;li&gt;&lt;span class="fa fa-phone"&gt;&lt;/span&gt; &lt;strong&gt;Telephone&lt;/strong&gt;: 0000-0000&lt;/li&gt;
                      &lt;li&gt;&lt;span class="fa fa-location-arrow"&gt;&lt;/span&gt; &lt;strong&gt;Location&lt;/strong&gt;: Address&lt;/li&gt;
  </code></pre>
  
  <p>How do I fix this?</p>