Simply rendering your Unity Application within your React Application is just the beginning! The Unity Context exposes a lot more fun functions and properties to play around with such as two way communication or requesting fullscreen or a pointerlock. The possibilities are endless, what's next is up to you!
I eventually ran into some limitations (accessing Camera Roll back then, also in-app purchases back then) that forced me to have to use more native stuff. I bet it's come a long way though since then.