Properly type children element

app/javascript/packs/frontend/components/layout/application_layout.tsx

@@ -6,7 +6,7 @@ import {Link} from 'react-router-dom';
 import './style';
 
 interface Props {
-  children?: React.ReactElement;
+  children?: React.ReactNode;
 }
 
 function ApplicationLayout({children}: Props): React.ReactElement {