Replace ambiguous code example in the documentation

[ryanzidago]

Hi all,

First thing first, thanks for this library and the tutorial.

The current wording is confusing: it says that the lines should be "added" to the Application.module function, but the code example underneath shows you the whole function, without the configureRouting() call which is necessary to access the graphql playground.

IMHO, we should simply tell the reader to either:

• replace the current Application.module function with whatever is displayed as a code example underneath (what I suggest in this PR)
• reformat the code example so as to make sure that this change is to be added to the Application.module and not to replace it for example:

fun Application.module(testing: Boolean = false) {
    // ...
    install(GraphQL) {
        playground = true
        schema { 
            query("hello") {
                resolver { -> "World" }
            }
        }
    }
}

In this PR, I chose the first option, as it is the most straightforward, less error prone and easy to follow.

[sangeetds]

Hi @ryanzidago
I think this would be a good update to the README.md. I have forked this repo and trying to maintain it. I thought it would be better if you could open the same PR at https://github.com/sangeetds/KGraphQL instead of me pushing your commit from there. Thanks!

[jeggy]

I'm approving this for now. But we should upgrade the ktor plugin the be available for ktor version 2.x and then update the tutorial to be written for ktor 2.x and using the new ktor project wizard.