fix: hide welcome screen on mobile once user interacts (#6185)

* fix: hide welcome screen on mobile once started drawing

* Add specs

src/tests/MobileMenu.test.tsx

@@ -0,0 +1,45 @@
+import ExcalidrawApp from "../excalidraw-app";
+import {
+  mockBoundingClientRect,
+  render,
+  restoreOriginalGetBoundingClientRect,
+} from "./test-utils";
+
+import { UI } from "./helpers/ui";
+
+describe("Test MobileMenu", () => {
+  const { h } = window;
+  const dimensions = { height: 400, width: 800 };
+
+  beforeEach(async () => {
+    await render(<ExcalidrawApp />);
+    //@ts-ignore
+    h.app.refreshDeviceState(h.app.excalidrawContainerRef.current!);
+  });
+
+  beforeAll(() => {
+    mockBoundingClientRect(dimensions);
+  });
+
+  afterAll(() => {
+    restoreOriginalGetBoundingClientRect();
+  });
+
+  it("should set device correctly", () => {
+    expect(h.app.device).toMatchInlineSnapshot(`
+      Object {
+        "canDeviceFitSidebar": false,
+        "isMobile": true,
+        "isSmScreen": false,
+        "isTouchScreen": false,
+      }
+    `);
+  });
+
+  it("should initialize with welcome screen and hide once user interacts", async () => {
+    expect(document.querySelector(".welcome-screen-center")).toMatchSnapshot();
+
+    UI.clickTool("rectangle");
+    expect(document.querySelector(".welcome-screen-center")).toBeNull();
+  });
+});