Publish an OpenAPI document describing the Swift.org API

[czechboy0]

Is your feature request related to a problem? Please describe

Tools that inspect the published list of releases, such as swiftly, need to manually maintain their Swift code for calling the API endpoints and parsing responses, such as: https://github.com/swiftlang/swiftly/blob/main/Sources/SwiftlyCore/HTTPClient.swift

As the Swift.org API evolves, keeping all clients in sync by hand is error-prone and time-consuming.

Describe the solution you'd like

We should publish an OpenAPI document describing the Swift.org API, allowing clients to generate their type-safe code easily in any languages using OpenAPI code generators, such as swift-openapi-generator.

Describe alternatives you've considered

Continue maintaining clients by hand, but that doesn't seem to be a good long term strategy.

Additional context

N/A

[czechboy0]

PR: #841