add order ui

app/javascript/elements/mount_on_click.js

@@ -0,0 +1,11 @@
+export default class extends HTMLElement {
+  connectedCallback () {
+    this.addEventListener('click', () => {
+      document.body.append(this.template.content)
+    })
+  }
+
+  get template () {
+    return document.getElementById(this.dataset.templateId)
+  }
+}