Add new step for easier graphql query

[mhlsf]

Add a step that by default set the method to post and the route for the request to /graphql.

Also Json encode the query into the graphQl wrapper.

[Taluu]

Had my eyes on this a short while ago, not sure if it is pertinent to have a graphql step to be honest, as a graphql reequest can be sent through a simple http request (with the graphql query as the body).