mail-addons/mail_check_immediately/views.xml

<openerp>
    <data>
        <template
            id="assets_backend_inherited_check_mail"
            name="Check mail immediately bar"
            inherit_id="web.assets_backend"
        >
            <xpath expr="." position="inside">
                <script
                    type="text/javascript"
                    src="/mail_check_immediately/static/src/js/main.js"
                />
            </xpath>
        </template>
    </data>
</openerp>