fix: update config reading for NBS

Signed-off-by: web-next-automation <web-platform@doordash.com>

docs/conf/reading.md

@@ -141,6 +141,37 @@ from `@backstage/core-plugin-api`.
 
 ## Accessing ConfigApi in Backend Plugins
 
-In backend plugins the configuration is passed in via options from the main
+### Old Backend System
+
+In the old backend system plugins, the configuration is passed in via options from the main
 backend package. See for example
 [packages/backend/src/plugins/auth.ts](https://github.com/backstage/backstage/blob/244eef851f5aa19f91c7c9b5c12d5df95cf482ca/packages/backend/src/plugins/auth.ts#L23).
+
+### New Backend System
+
+In the new backend system, plugins are able to directly access config through dependencies. You can access config like so,
+
+```ts title="plugins/your-plugin-backend/src/plugin.ts"
+export const yourPlugin = createBackendPlugin({
+  pluginId: 'yourPlugin',
+  register(env) {
+    env.registerInit({
+      deps: {
+        httpRouter: coreServices.httpRouter,
+        logger: coreServices.logger,
+        // highlight-next-line
+        config: coreServices.rootConfig,
+      },
+      async init({
+        httpRouter,
+        logger,
+        // highlight-next-line
+        config,
+      }) {
+        // highlight-next-line
+        console.log(config.getOptionalString('backend.test.property'));
+      },
+    });
+  },
+});
+```