add language button
this code is default module code website_report module
<xpath expr="//footer" position="replace">
<ul class="list-inline js_language_selector mt16" t-if="(request and request.website_multilang and len(languages) > 1) or (website and editable)">
<li t-foreach="languages" t-as="lg">
<a t-att-href="url_for(request.httprequest.path + '?' + keep_query(), lang=lg[0])" t-att-data-lang="lg[0]"
t-att-data-default-lang="editable and 'true' if website and lg[0] == website.default_lang_code else None"> <t t-esc="lg[1].split('/').pop()"/> </a> </li> <li groups="base.group_website_publisher"> <t t-set="url_return" t-value="url_for('', '[lang]') + '?' + keep_query()"/> <a t-attf-href="/web#action=base.action_view_base_language_install&website_id=#{website.id if website else ''}&url_return=#{url_return}"> <i class="fa fa-plus-circle"/> Add a language...
</a>
</li>
</ul>
</xpath>
