Add graphql version 14 into peer deps to avoid `has incorrect peer dependency` warning

[Jose Javier Vega]

Hi, I'm using the graphiql-explorer with graphql version 14 and it all works fine, but when building, or installing deps, it shows a warning saying @graphiql-explorer@0.4.3 has incorrect peer dependency.... So if it newer versions are added into peerDependencies then warning will go away. I can also send a PR if needed.

Thanks

[Alan Poulain]

The PR already exists: #16.

[Jose Javier Vega]

That's great, thanks!