web/web_widget_prefixed_url/views/template.xml

<odoo>
    <!-- Prefixed Widget Asset-->
    <template id="assets_widget_prefixed_url" inherit_id="web.assets_backend"
              name="Widget Prefixed URL assets">
        <xpath expr="." position="inside">
            <script type="text/javascript"
                    src="/web_widget_prefixed_url/static/src/js/widget_prefixed_url.js"/>
        </xpath>
    </template>

</odoo>