Update README.md

Signed-off-by: Niklas Aronsson <niklasar@axis.com>

.changeset/forty-kids-do.md

@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-airbrake': patch
+---
+
+Added documentation for the [new backend system](https://backstage.io/docs/backend-system/)

plugins/airbrake/README.md

@@ -98,17 +98,6 @@ The Airbrake plugin provides connectivity between Backstage and Airbrake (https:
    }
    ```
 
-   ```typescript
-   // Using the new backend system
-   import { airbrakePlugin } from '@backstage/plugin-airbrake-backend';
-
-   const backend = createBackend();
-   backend.add(airbrakePlugin());
-   // ... other feature additions
-
-   backend.start();
-   ```
-
 6. Add this config as a top level section in your `app-config.yaml`:
 
    ```yaml
@@ -127,6 +116,21 @@ The Airbrake plugin provides connectivity between Backstage and Airbrake (https:
        airbrake.io/project-id: '123456'
    ```
 
+#### New Backend System
+
+The Airbrake backend plugin has support for the [new backend system](https://backstage.io/docs/backend-system/), here's how you can set that up:
+
+In your `packages/backend/src/index.ts` make the following changes:
+
+```diff
+  import { createBackend } from '@backstage/backend-defaults';
++ import { airbrakePlugin } from '@backstage/plugin-airbrake-backend';
+  const backend = createBackend();
+  // ... other feature additions
++ backend.add(airbrakePlugin());
+  backend.start();
+```
+
 ## Local Development
 
 Start this plugin in standalone mode by running `yarn start` inside the plugin directory. This method of serving the plugin provides quicker