Couldn't generate from a schema with +1 and -1 in the same struct

[kenkoooo]

Thank you so much for creating an awesome library! It helped me a lot. I found the following issue while using it.

schemafy couldn't generate a schema of GitHub webhook event payloads because of duplicated field declaration. The root cause is that the schema has fields +1 and -1 in the same struct, and schemafy converts both to _1.

schema: https://unpkg.com/@octokit/[email protected]/schema.json