Allow multiple 2XX responses on a single endpoint

[amerritt14]

I'd like to be able to specify multiple different 2XX responses on a single endpoint. For instance, a 200 + 202 response.

OpenAPI has a responses array where you can specify whatever you like, but fern definitions appear to only allow a single 2XX response, while everything else must be listed under errors. Listing a 2XX as an error feels wrong. The right solution would be to allow multiple 2XX responses.