Add file-group-page component

app.js

@@ -1,5 +1,6 @@
 import { Layout } from "/components/layout.js"
 import { Page } from "/components/page.js"
+import { FileGroupPage } from "/components/file-group-page.js"
 import { Header } from "/components/header.js"
 import { NavMenu } from "/components/nav-menu.js"
 import { Dialog } from "/dialog/dialog.js"
@@ -8,6 +9,9 @@ import { Dropdown } from "/menu/dropdown.js"
 
 customElements.define('m-layout', Layout)
 customElements.define('m-page', Page)
+customElements.define(
+  'm-file-group-page', FileGroupPage
+)
 customElements.define('m-header', Header)
 customElements.define('m-nav-menu', NavMenu)
 customElements.define('m-dialog', Dialog)