Here is a snippet from a site I made:

    <zjs-include remote-src='/project/webroot/zjsi/navbar-signed-in.zjsi'></zjs-include>
    <zjs-include remote-src='/project/webroot/zjsi/error-dialog.zjsi'></zjs-include>
    <zjs-include remote-src='/project/webroot/zjsi/info-dialog.zjsi'></zjs-include>

So, yeah, you don't need server-side includes if you use one of many free client-side webcomponent. That component `zjs-include` took me 30m to write.