pos/pos_order_load/view/pos_order_load.xml

<?xml version="1.0" encoding="utf-8"?>
<odoo>
    <template id="assets_backend" name="pos_order_load assets" inherit_id="web.assets_backend">
        <xpath expr="." position="inside">
            <script type="text/javascript" src="/pos_order_load/static/src/js/pos_order_load.js"></script>
        </xpath>
    </template>
    <template id="index_pos_order_load" name="POS Index Order Load" inherit_id="point_of_sale.index">
        <xpath expr="//head" position="inside">
            <link rel="stylesheet" href="/pos_order_load/static/src/css/pos_order_load.css"/>
        </xpath>
    </template>
</odoo>