support enums in orphanedTypes

[zoltan-mihalyi]

Is your feature request related to a problem? Please describe.

I had to add orphaned types, including an enum type.

Describe the solution you'd like

Make orphanedTypes config accept enum values, or add an orphanedEnums config

Describe alternatives you've considered

Monkey-patch SchemaGenerator.buildOtherTypes, to handle enums

[MichalLytek]

What is your use case of declaring enum that you do not use in your schema?

[zoltan-mihalyi]

In general, think the use case is the same as for object types. For my specific use case, I am using schema stitching, and want to declare an enum using type-graphql, which for i do not use in the local schema, but only in the stitched schema.
I can declare it in the stitched schema only, but then I do not have a TypeScript object, where I can use the enum values