[Docs] Running a development server is missing what's expected when the request is sent

[javorszky]

https://atmo.suborbital.dev/getstarted/building-and-running

This section:

You can test the /hello route in a second terminal by sending a POST request with a body to it:

curl localhost:8080/hello -d 'from the Kármán line!'

I think it is a good idea to explicitly state that a successful test should return a 200 with the body returned to you, and everything else needs to be looked at.