implemented balance headers

src/layouts/index.ts

@@ -1 +1,2 @@
 export * from "./menu-layout/MenuLayoutElement";
+export * from "./initial-layout/InitialLayoutElement";

src/layouts/initial-layout/InitialLayoutElement.ts

@@ -0,0 +1,31 @@
+import { controller, target } from "@github/catalyst";
+import { closest } from "core/utils";
+import { html, TemplateResult } from "@github/jtml";
+import { BaseLayoutElement } from "common/layouts";
+import { AppMainElement } from "components/";
+
+@controller
+class InitialLayoutElement extends BaseLayoutElement {
+    @closest appMain: AppMainElement;
+    @target appPage: HTMLDivElement;
+
+    constructor() {
+        super();
+    }
+
+    elementConnected = (): void => {
+        this.update();
+    };
+
+    elementDisconnected = (appMain: AppMainElement): void => {};
+
+    render = (): TemplateResult => {
+        return html`
+            <div data-target="initial-layout.appPage">
+                <app-slot data-target="initial-layout.appSlot"></app-slot>
+            </div>
+        `;
+    };
+}
+
+export type { InitialLayoutElement };