Fix tutorial instruction

Changed `npm start` -> `npm run dev`

`npm start` throws an error since it isn't a defined run script

I used the more verbose syntax to make it more obvious the user is calling a run script, not running an npm command named "dev"

Author: ianjmacintosh

src/content/docs/pages/tutorials/build-an-api-with-pages-functions/index.mdx

@@ -35,7 +35,7 @@ In your terminal, create a new React project called `blog-frontend` using the `c
 ```sh title="Create a new React application"
 npx create-vite -t react blog-frontend
 cd blog-frontend
-npm start
+npm run dev
 ```
 
 ### Set up your React project