Added routes and links on the menu page.
Notes:
<Link to="/topics">Topic</Link>
<button onClick={()=>props.history.push("/topics")}>Topic</button>
<Link to={`${props.match.url}/ParticularTopic`}>ParticularTopic</Link>Also add a rough sketch on showing the stock item react components.
https://gunpla-shop.huatzhi.repl.co/
Spent some time on understanding Heap, B-Tree, stacks and queues.