feat: support WelcomeScreen customization API (#6048)

src/components/welcome-screen/WelcomeScreen.tsx

@@ -0,0 +1,17 @@
+import { Center } from "./WelcomeScreen.Center";
+import { MenuHint, ToolbarHint, HelpHint } from "./WelcomeScreen.Hints";
+
+import "./WelcomeScreen.scss";
+
+const WelcomeScreen = (props: { children: React.ReactNode }) => {
+  // NOTE this component is used as a dummy wrapper to retrieve child props
+  // from, and will never be rendered to DOM directly. As such, we can't
+  // do anything here (use hooks and such)
+  return null;
+};
+WelcomeScreen.displayName = "WelcomeScreen";
+
+WelcomeScreen.Center = Center;
+WelcomeScreen.Hints = { MenuHint, ToolbarHint, HelpHint };
+
+export default WelcomeScreen;