* feat(ui): configure default expansion depth for models
This commit adds possibility to configure defaultModelsExpandDepth,
which controls how models (at the bottom of the API doc) are displayed.
Default value is 1, but it can be set to -1 completely hide the models.
https://github.com/swagger-api/swagger-ui/blob/master/docs/usage/configuration.md#display
* doc: update README.md
Added Configuration section describing available configuration options.