Add hint for storing data on-disc via app-config.yaml

docs/9-platform-engineering/9.1-backstage.md

@@ -79,6 +79,16 @@ a GitHub org to play around with. Each person going through the bootcamp will ne
     - Deep Dive: Apply a custom theme
 4. Push your instance of Backstage to a repo in your new GitHub Organization
 
+  ?> By default, your Backstage instance will be configured to use SQLite to store data in-memory. If you would like your instance's data to be stored to your disc, you can specify a folder in your `app-config.yaml` as follows:
+  ```  database:
+    client: better-sqlite3
+    # sqlite is configured by default to store in-memory
+    connection: # ':memory:'
+      directory: 'abs/path/to/this-file/data/backstage.sqlite'
+```
+
+
+
 ### Exercise 3: Configure Authentication via GitHub
 
 Currently your Backstage instance is not authenticating the user. You are an anonymous guest. Given that an IDP will have access to all the engineering resources in an organization and have access to self-service resources we need to add authentication. Backstage's authentication system serves a couple of purposes. First it is there for sign-in functionality and to authenticate the user. Additionally it can be used to grant access to third-party resources. Typically you will use one authentication provider for sign-in functionality and other authentication providers will be used to grant access to third-party resources.