web/web_timeline/views/web_timeline.xml

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

    <template id="assets_backend" name="web_timeline assets" inherit_id="web.assets_backend">
        <xpath expr="." position="inside">
            <link rel="stylesheet" href="/web_timeline/static/lib/vis/vis-timeline-graph2d.min.css"/>
            <link rel="stylesheet" href="/web_timeline/static/src/css/web_timeline.css"/>

            <script type="text/javascript" src="/web_timeline/static/lib/vis/vis-timeline-graph2d.min.js"/>
            <script type="text/javascript" src="/web_timeline/static/src/js/timeline_view.js"/>
            <script type="text/javascript" src="/web_timeline/static/src/js/timeline_renderer.js"/>
            <script type="text/javascript" src="/web_timeline/static/src/js/timeline_controller.js"/>
            <script type="text/javascript" src="/web_timeline/static/src/js/timeline_model.js"/>
            <script type="text/javascript" src="/web_timeline/static/src/js/timeline_canvas.js"/>
        </xpath>
    </template>

</odoo>