Add GitHubRestAPISwiftOpenAPI

[Wei18]

• Project Name: GitHubRestAPISwiftOpenAPI
• Project URL: https://github.com/Wei18/github-rest-api-swift-openapi
• Project Description: Scheduled generated GitHub's REST API as Swift code from OpenAPI specification.
• Why it should be added to awesome-swift: Use Github Dependabot version updates to combine both github/rest-api-description and apple/swift-openapi-generator, make Github API Swift code & Swift Docc always auto up-to-date.
• At least 15 stars (GitHub project)
• Support Swift 5
• Updated contents.json instead of README
• Lib is fully open sourced, written in Swift and not a wrapper over compiled lib
• Description does not say "written in Swift" or variant 🤓

[matteocrippa]

@Wei18 thank you for your submission, I see we are getting close to the 15 ⭐ so later we can proceed merging