Feature Request: Support Open API Extensions for branding purposes

[tinacious]

Thanks for this great library! 🙏

Open API Extensions are supported by some doc generators like Redoc and allow us to add branding, e.g. x-logo. It would be great if we can add this in the Dox configuration, perhaps namespaced under extensions or similar, for example:

Dox.configure do |config|
  # ...

  config.extensions['x-logo'] = {
    "url": "https://example.com/logo.png",
    "backgroundColor": "#ff3399"
  }

  # ...
end

I was able to add support for automated branding afterwards with the following script:

#!/usr/local/bin/ruby
require 'json'

docs = File.read('spec/api_doc/v1/schemas/docs.json')
docs_json = JSON.parse(docs)

docs_json['info']['x-logo'] = {
  "url": "https://example.com/logo.png",
  "backgroundColor": "#ff3399"
}

updated_docs = JSON.pretty_generate(docs_json)

File.write('spec/api_doc/v1/schemas/docs.json', updated_docs)

Script reference

Thanks again for all your great work on this library.