fix: PageInfo must define one or more fields
fix: PageInfo must define one or more fields

Fixes a regression introduced in `v3.1`. `schemaComposer.createObjectTC` accepts a `typeDef`, which could be a `string` (as in https://github.com/graphql-compose/graphql-compose-elasticsearch/blob/v3.1.1/src/resolvers/searchConnection.js#L141). `cfg` does not have `field` attributes in this case, causing `PageInfo` to be empty.

Closes #60
nodkz/graphql-compose-elasticsearch