Fix component closure and document technical details

Added closing brace for the component definition and included key technical considerations about recursive components.

Author: ps0305

Coding Interview Prep/fileSystem.md

@@ -55,7 +55,8 @@ export default function App() {
       <FileExplorerItem node={fileSystem} />
     </div>
   );
-}```
+}
+```
 
 ### Key Technical Considerations
 * Recursive Components: The FileExplorerItem component calls itself if the node isFolder is true. This is the standard way to handle trees of arbitrary depth.