Update react-md url for with-react-md (#15325)

Low hanging fruit 🍎 
Resolves: #15321

`https://react-md.mlaursen.com/` -> `https://react-md.dev/`

examples/with-react-md/README.md

 # Example app with react-md
 
-This example features how you use [react-md](https://react-md.mlaursen.com/) (React Material Design) with Next.js.
+This example features how you use [react-md](https://react-md.dev/) (React Material Design) with Next.js.
 
 I recommend reading [layout-component](../layout-component) example next to learn how to reuse the layout across the pages.