You have to add the UI5 service routing in the application descriptor file (neo-app.json) of your HTML5 application -> Accessing SAPUI5 Resources.
If you uses "/resources" as application path (like in the linked example) you can use it in your bootstrap tag like following:
<script id="sap-ui-bootstrap" src="/resources/sap-ui-core.js"></script>
Regards,
Florian