Update Tooling

[uwap]

A lot of the tooling is currently outdated and contains security vulnerabilities.

• Replaces swagger-repo by redocly
  • Swagger-Repo is no longer maintained
  • Redocly generates the Redoc documentation and allows linting of the specs
  • See the todo list below about swagger-ui
  • I have not been able to find a different approach to starting swagger-editor, therefore I've also removed gulp as a dependency
• Removes shelljs
  • The build script has been replaced by Redocly entirely
  • The deploy branch script has been rewritten in bash instead
• Removes gulp
  • gulp is no longer needed

To Do:

• Replace deploy-to-gh-pages as it is not maintained
• Add new tooling to build the Swagger UI output. Swagger-Repo used to do that. For now, only the Redoc and the openapi.yaml and openapi.json are generated.