knowledge/document_url/view/document_url_view.xml

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

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

    <record model='ir.actions.act_window' id='action_ir_attachment_add_url'>
        <field name='name'>Add URL</field>
        <field name='res_model'>ir.attachment.add_url</field>
        <field name='type'>ir.actions.act_window</field>
        <field name='target'>new</field>
        <field name='view_type'>form</field>
        <field name='view_mode'>form</field>
    </record>

    <record model="ir.ui.view" id="view_ir_attachment_add_url_form">
        <field name="name">ir.attachment.add_url.form</field>
        <field name="model">ir.attachment.add_url</field>
        <field name="arch" type="xml">
            <form string="Add URL">
                <group>
                    <field name="name"/>
                    <field name="url" widget="url"/>
                </group>
                <footer>
                    <button name="action_add_url" string="Add" class="oe_highlight" type="object" />
                    or
                    <button special="cancel" string="Cancel" class="oe_link" />
                </footer>
            </form>
        </field>
    </record>

</odoo>