eiru_num2word/templates.xml

<openerp>
    <data>
        <!-- Templates -->
        <template id="eiru_num2word" inherit_id="web.assets_backend">
             <xpath expr="." position="inside">
                <script type="text/javascript" src="/eiru_num2word/static/src/js/num2Word.js" />
             </xpath>
        </template>
    </data>
</openerp>