Feature/customizable UI config

[john-pope]

There are many options in the swagger ui configuration that can't currently be set. This update allows setting most parameters that are listed in the SwaggerUI configuration documentation (simple values only, no functions or variable values)

This would allow for handling scenarios reported in issues #9 and #18 like this:

swagger_doc_config = { "validationUrl": None, "displayRequestDuration": True }

api_doc(app, config_path='/config/test.yaml', title='API doc', doc_config=swagger_doc_config)

[PWZER]

Supported，Thank you!