[feature_request] Add language data under user object in the GraphQL API

[rickstaa]

There is currently no way to fetch the languages a specific user uses. The current repositories/languages object of the GraphQL API will return the languages of a repository. Allowing users to fetch the user language data directly under the user object would improve the GraphQL API. It would provide users with more accurate Language proficiency information and improve the stats displayed by repositories like github-readme-stats. I'm unsure if this is technically possible given the current GraphQL design and performance requirements and the linguist tool, but here is my proposal.

Related to: #18230

Current behaviour

Current graphQL query:

query userInfo($login: String!) {
  user(login: $login) {
    repositories(ownerAffiliations: OWNER, isFork: true, first: 100) {
      nodes {
        name
        languages(first: 10, orderBy: {field: SIZE, direction: DESC}) {
          edges {
            size
            node {
              color
              name
            }
          }
        }
      }
    }
  }
}

Current GraphQL variables

{"login": "rickstaa"}

This will return the language stats per repository.

New behaviour

Maybe an attribute like isUser: true could be added for fetching user-specific language information.

New graphQL query:

query userInfo($login: String!) {
  user(login: $login) {
    languages(first: 10, orderBy: {field: SIZE, direction: DESC}, isUser: true) {
      edges {
        size
        node {
          color
          name
        }
      }
    }
  }
}

New GraphQL variables

{"login": "rickstaa"}