web/web_widget_digitized_signature/views/web_digital_sign_view.xml

<odoo>

    <template id="web_widget_digitized_signature_backend" name="web_widget_digitized_signature assets" inherit_id="web.assets_backend">
        <xpath expr="." position="inside">
            <script type="text/javascript"
                    src="/web_widget_digitized_signature/static/src/js/digital_sign.js"/>
        </xpath>
    </template>

</odoo>