feat: add authorization

[tobiasdiez]

Fixes #4.

Todo:

• Make subtypes for return values work
• Add tests
• Cleanup code
• Add fallback error https://github.com/dimatill/graphql-shield/blob/ac38cc0c2e53f2835d44287f4d0e5a9132372f57/packages/graphql-shield/src/generator.ts#L72
• Answer https://stackoverflow.com/questions/74453847/typescript-lower-bound-of-function-parameter-decorator