fix: markdown format for the blog-starter example (vercel#37792)

## Documentation / Examples

The markdown format for blog-starter example was broken, so fixed it.


- [x] Make sure the linting passes by running `pnpm lint`
  It failed, without my changes.
- [x] The examples guidelines are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing.md#adding-examples)

examples/blog-starter/README.md

@@ -39,24 +39,18 @@ Deploy the example using [Vercel](https://vercel.com?utm_source=github&utm_mediu
 
 Execute [`create-next-app`](https://github.com/vercel/next.js/tree/canary/packages/create-next-app) with [npm](https://docs.npmjs.com/cli/init), [Yarn](https://yarnpkg.com/lang/en/docs/cli/create/), or [pnpm](https://pnpm.io) to bootstrap the example:
 
-```
+```bash
 npx create-next-app --example blog-starter blog-starter-app
-
-```
-
-or
-
-```
+# or
 yarn create next-app --example blog-starter blog-starter-app
 # or
 pnpm create next-app --example blog-starter blog-starter-app
-
 ```
 
 Your blog should be up and running on [http://localhost:3000](http://localhost:3000)! If it doesn't work, post on [GitHub discussions](https://github.com/vercel/next.js/discussions).
 
 Deploy it to the cloud with [Vercel](https://vercel.com/new?utm_source=github&utm_medium=readme&utm_campaign=next-example) ([Documentation](https://nextjs.org/docs/deployment)).
 
-# Notes
+## Notes
 
 This blog-starter uses [Tailwind CSS](https://tailwindcss.com) [(v3.0)](https://tailwindcss.com/blog/tailwindcss-v3).