pos/pos_picking_load/views/pos_picking_load.xml

<?xml version="1.0" encoding="utf-8"?>

<odoo>

    <template id="assets" inherit_id="point_of_sale.assets">
        <xpath expr="." position="inside">
            <script type="text/javascript" src="/pos_picking_load/static/src/js/widget.js"></script>
            <script type="text/javascript" src="/pos_picking_load/static/src/js/model.js"></script>
        </xpath>
    </template>

    <template id="index" inherit_id="point_of_sale.index">
        <xpath expr="//head" position="inside">
            <link rel="stylesheet" href="/pos_picking_load/static/src/css/pos_picking_load.css"/>
        </xpath>
    </template>

</odoo>