Inject swagger UI to documentation of oxauth (same as in oxd docs)

[yuriyz]

Inject swagger UI to documentation of oxauth (same as in oxd docs).

We have swagger spec on oxauth side since 4.2: https://raw.githubusercontent.com/GluuFederation/oxAuth/master/docs/oxAuthSwagger.yaml

We should show it in documentation same as in oxd case here.

Standalone swagger UI: https://gluu.org/swagger-ui/?url=https://raw.githubusercontent.com/GluuFederation/oxAuth/master/docs/oxAuthSwagger.yaml