Multiple Authentication Type Support

[ggpwnkthx]

https://github.com/Dorthu/openapi3/blob/2580c603051fa459771ca08efee90aae508be4ec/openapi3/openapi.py#L86

Multiple authentication types is supported by the OpenAPI spec, but this line prevents that from being possible. Changing it to the following fixes it:

self._security.update({security_scheme: value})

[commonism]

Additionally you can have a requirement for multiple authentication providers - like username & password. https://aiopenapi3.readthedocs.io/en/latest/advanced.html#authentication