social/mail_forward/views/assets.xml

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

<!-- © 2014-2015 Grupo ESOC <www.grupoesoc.es>
     License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html). -->

<odoo>

    <template id="assets_backend"
              name="Mail forward assets"
              inherit_id="web.assets_backend">
        <xpath expr="." position="inside">
            <link rel="stylesheet" href="/mail_forward/static/src/css/mail_forward.less" type="text/less"/>
            <script type="text/javascript" src="/mail_forward/static/src/js/mail_forward.js"/>
        </xpath>
    </template>

</odoo>