Fix undefined resolveType issue

[adelsz]

Interface and union types resolveType resolution was broken.
GraphQLInterfaceType, GraphQLUnionType were missing the resolveType after joinMonsterAdapt. This happened because resolveType field should be set at type level and not in type._typeConfig.

[frederikhors]

@adelsz is this related to this? #12

[adelsz]

@frederikhors I don't think so. type._typeConfig is defined in this case.

[lorensr]

@adelsz is this still an issue in the 0.1.0 version I just published?

[lorensr]

It includes these changes:

https://github.com/acarl005/join-monster-graphql-tools-adapter/pull/15/files

[adelsz]

Unfortunately, I won't be able to check this any time soon.
But it shouldn't be too hard to check/reproduce with a mock GraphQLInterfaceType