docs: add documentation and examples for sqlc.narg

[skabbes]

To complete the sqlc.narg feature defined here: #1536

Feel free to edit / make your own my tone / wording.

[skabbes]

@kyleconroy can you pay special attention to this:
b9efe90

I am not sure if it was the right thing to do, but it seemed completely unused (or at least unneeded)

Could you also review the recommitting of the python and kotlin examples. I tried to fix a kotlin issue, but I have no idea what the correct kotlin should be. Maybe @mightyguava is around to advise?

[skabbes]

Given the build issues I am having, I isolated the documentation only (no examples) here

[kyleconroy]

I also don't know Kotlin super well. Will take me quite a bit to review this one.

[skabbes]

I think we can likely just close this then. Anyone trying to use sqlc.narg (or sqlc.arg for that matter) + kotlin will have issues, but at that point we'll have a Kotlin expert to weigh in and advise.

[mightyguava]

Sorry, I didn’t quite end up getting adoption this on my side either. 😞