path: root/ab_openstreetmap/views/templates.xml

<odoo>
  <data>
    <template id="assets_backend" inherit_id="web.assets_backend">
      <xpath expr="." position="inside">
        <script type="text/javascript" src="/ab_openstreetmap/static/src/js/googlemap_widget.js"/>
      </xpath>
    </template>
  </data>
</odoo>