The nteract repo uses some fonts that you'll need to manually include:
<link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:200,300,400,500,600,700,900|Source+Sans+Pro:200,200i,300,300i,400,400i,600,600i,700,700i,900,900i" rel="stylesheet">
Make sure to include those font-weight options or text may not get the right emphasis!