pos/pos_restricted_customer_list/views/assets_backend.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright 2017-2019 Therp BV <https://therp.nl>
     License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl). -->

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