[Proposal] Integrated API caller.

After reviewing docfx templates and plugins, i couldn't find integrated api caller. I think that integrated api caller feature is benefical for developers. After generating docfx website for api projects with this potential feature, developers can makes POST,GET,PUT etc. requests to endpoints and they can sets header, body etc. to their requests easily. They don't spend extra effort with opening swagger, postman or other tools to make requests to api.

**Expected Behavior**:
If developers set attribute to their controller class or methods about whether showing integrated api caller or not, inside of docfx website, integrated api caller section will be showed. Also, developers should set parameters like `[Consumes("application/json")]`, `[Produces("application/json")]`, DTO for controller methods for setting default placeholder parameters to integrated api caller requests.