Material icons aren't rendered as icons but as words

The html rendering within the moodle app doesn't currently support material icons (initially developed by Google) and now found at https://material.io/tools/icons/

This icon collection allowed for a special use of fonts and <i> tags with material-icon classes.
Examples:
<link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
<i class="material-icons">person</i><br>
<i class="material-icons">email</i><br>
<i class="material-icons">phone</i></br>
<i class="material-icons">schedule</i>
In the app, the words appear instead of the icons.