message: Error with duplicate operation names
diff: - <First `apollo-graphql` related entry goes here>
  - `apollo-language-server`
  - Add debugging util classes for better error/warning handling [#1429](https://github.com/apollographql/apollo-tooling/pull/1429)
  + - Add error for duplicate client operation names [#1466](https://github.com/apollographql/apollo-tooling/pull/1466)
  - `apollo-tools`
  - <First `apollo-tools` related entry goes here>
  - `vscode-apollo`
  