apollo-language-server: Include graphql as a peer dependency

[HishamAli81]

Intended outcome:

Graphql to be included as a peer dependency in the apollo-language-server package, similar to how it's included in the apollo-graphql package (https://github.com/apollographql/apollo-tooling/blob/master/packages/apollo-graphql/package.json#L19).

Nice to have: Add support for GraphQL 16.

Actual outcome:

Graphql is currently being included as a dependency in the apollo-language-server package (https://github.com/apollographql/apollo-tooling/blob/master/packages/apollo-language-server/package.json#L37), and doesn't follow these guidelines: https://leebyron.com/graphql-js-preparing-for-v14/

Versions

apollo-language-server: 1.26.9