New rule: avoid duplicate fields in operations

[FluorescentHallucinogen]

It should suggest remove duplicate fields, input fields, arguments, etc.

As an option, it can suggest to use GraphQL aliases for duplicate fields instead of removing them.

[dotansimha]

@FluorescentHallucinogen Not sure I understood. Example for incorrect code?
Thanks!

[FluorescentHallucinogen]

query getUsers {
  users {
    id
    firstName
    lastName
    username
    phone
    email
    github
    email #twice
    twitter
  }
}

This already implemented in graphql-prettier.

[ilyavolodin]

https://github.com/dotansimha/graphql-eslint/blob/master/docs/rules/prettier.md

[FluorescentHallucinogen]

query getUsers {
  users(
    first: 100
    skip: 50
    after: "cji629tngfgou0b73kt7vi5jo"
    first: 100 # duplicate argument
  ) {
    id
  }
}

[dotansimha]

Implemented in: #245

[dotansimha]

Available in @graphql-eslint/eslint-plugin@0.7.0