[OpenAPI] - Update Usage

Author: keyz182

docs/usage.md

@@ -954,6 +954,26 @@ class MyViewSet(ModelViewSet):
     schema = AutoSchema(openapi_schema=openapi_schema)
 ```
 
+### Get Schema in View
+
+Add the following to `urls.py`, to expose the schema at `/openapi`. This can be consumed by (Swagger UI)[https://swagger.io/tools/swagger-ui/] or other tools.
+```python
+from rest_framework.schemas import get_schema_view
+from rest_framework_json_api.schemas.openapi import SchemaGenerator
+
+...
+
+urlpatterns = [
+    path('openapi', get_schema_view(
+        title="Example API",
+        description="API for all things …",
+        version="1.0.0",
+        generator_class=SchemaGenerator
+    ), name='openapi-schema'),
+    ...
+]
+```
+### Get Schema on Command Line
 To generate an OAS schema document, use something like:
 
 ```text