refactor(client/ts): port a few more widgets

src/public/app/widgets/containers/root_container.ts

@@ -0,0 +1,11 @@
+import type BasicWidget from "../basic_widget.js";
+import FlexContainer from "./flex_container.js";
+
+export default class RootContainer extends FlexContainer<BasicWidget> {
+    constructor(isHorizontalLayout: boolean) {
+        super(isHorizontalLayout ? "column" : "row");
+
+        this.id("root-widget");
+        this.css("height", "100dvh");
+    }
+}