make two lines a codeblock instead of inline code

Author: chrisweb

app/web_development/tutorials/next-js-static-first-mdx-starterkit/package-json-scripts/page.mdx

@@ -128,11 +128,15 @@ In our run script we use two hyphen (`--`) tho indicate that it is the end of th
 
 For example to launch the dev server on port 4000 without editing the package.json we could us this command:
 
-`npm run dev -- -p 4000`
+```shell
+npm run dev -- -p 4000
+```
 
 Or to start the production server:
 
-`npm start -- -p 4000`
+```shell
+npm start -- -p 4000
+```
 
 ## Next.js CLI commands and NPM npx