chore: add example for scalar and directive

[maapteh]

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This is a start on documenting the option for scalars and directives. Please note that the used approach like a common module is personally. Also i used Apollo as an example, not sure if its clear (maybe more examples, or more text needed?).

I dont know if i should put my own common approach like so in these docs. Because some can opt for a 'directives' module for example, or whatever. So any advise to make it more generic is welcome!

relates to #1650