docs: add data and persistence (#83)

README.md

@@ -108,6 +108,48 @@ The emulator is compatible with the following operations:
 | List (Select Fields)     | ❌ |
 | List (Time-Based Access) | ❌ |
 
+## Data
+
+The emulator stores configuration settings in a [SQLite](https://sqlite.org) database.
+
+The data that is generated by the emulator during a session may be persisted between sessions using a [volume](https://docs.docker.com/storage/volumes).
+
+```yaml
+services:
+  azure-app-configuration-emulator:
+    build:
+      context: https://github.com/tnc1997/azure-app-configuration-emulator.git
+      dockerfile: ./src/AzureAppConfigurationEmulator/Dockerfile
+    volumes:
+      - azure-app-configuration-emulator:/var/lib/azureappconfigurationemulator
+volumes:
+  azure-app-configuration-emulator:
+```
+
+The connection string for the database may be overridden using the environment variable `ConnectionStrings__DefaultConnection`.
+
+```yaml
+services:
+  azure-app-configuration-emulator:
+    build:
+      context: https://github.com/tnc1997/azure-app-configuration-emulator.git
+      dockerfile: ./src/AzureAppConfigurationEmulator/Dockerfile
+    environment:
+      - ConnectionStrings__DefaultConnection=Data Source=/var/lib/azureappconfigurationemulator/emulator.db
+```
+
+The database may be seeded with data and mounted into the container however care should be taken to ensure that the database has the required schema.
+
+```yaml
+services:
+  azure-app-configuration-emulator:
+    build:
+      context: https://github.com/tnc1997/azure-app-configuration-emulator.git
+      dockerfile: ./src/AzureAppConfigurationEmulator/Dockerfile
+    volumes:
+      - ./emulator.db:/var/lib/azureappconfigurationemulator/emulator.db
+```
+
 ## Messaging
 
 The emulator integrates with Azure Event Grid to publish events using the [Event Grid event schema](https://learn.microsoft.com/en-us/azure/event-grid/custom-topics#event-grid-event-schema) when configuration settings are deleted or modified.