Update config (#1903)

* New aproach for uploading sanic app config.

* Update config.rst

Co-authored-by: tigerthelion <bjt.thompson@gmail.com>
Co-authored-by: Adam Hopkins <admhpkns@gmail.com>

sanic/app.py

@@ -1452,3 +1452,13 @@ class Sanic:
         self.asgi = True
         asgi_app = await ASGIApp.create(self, scope, receive, send)
         await asgi_app()
+
+    # -------------------------------------------------------------------- #
+    # Configuration
+    # -------------------------------------------------------------------- #
+    def update_config(self, config: Union[bytes, str, dict, Any]):
+        """Update app.config.
+
+        Please refer to config.py::Config.update_config for documentation."""
+
+        self.config.update_config(config)