Add cql_if and cql_increment examples to GraphQL schema-first

[polandll]

Feedback from Ivan:

Documentation
The example for the schema upload using cURL was not working for me.
Wanted to use the @clq_increment directive, but I found no example of it. In the end I still did not implement the feature I would need it for, because I don’t know how to use the directive.
In general, very well documented, was missing examples on @cql_if and more about clustering columns.