Update README.md

Author: eadwinCode

README.md

@@ -221,7 +221,25 @@ class CarModule(ModuleBase):
         pass
 ```
 
+## Registering Module
+Ellar is not aware of `CarModule` yet, so we need to add it to the `modules` list of `ApplicationModule` at the `carsite/root_module.py`.
+```python
+from ellar.common import Module, exception_handler
+from ellar.core import ModuleBase
+from ellar.core.connection import Request
+from ellar.core.response import JSONResponse, Response
+
+from ellar.samples.modules import HomeModule
+from .apps.car.module import CarModule
 
+
+@Module(modules=[HomeModule, CarModule])
+class ApplicationModule(ModuleBase):
+    @exception_handler(404)
+    def exception_404_handler(cls, request: Request, exc: Exception) -> Response:
+        return JSONResponse(dict(detail="Resource not found."))
+
+```
 ## Enabling OpenAPI Docs
 To start up openapi, we need to go back to project folder in the `server.py`
 then add the following below.