improve readme

Dockerfile

@@ -1,4 +1,4 @@
-FROM varnish:fresh-alpine
+FROM varnish:7.5.0-alpine
 
 # install build dependencies
 USER root

README.md

@@ -1,12 +1,43 @@
 # Shopware Varnish Docker image
 
 The image bases on the official [Varnish image](https://hub.docker.com/_/varnish) and contains the Shopware default VCL.
+The containing VCL is for the usage with xkeys.
 
-## Additional environment variables
+<details>
+  <summary>Config for Shopware 6.6</summary>
+
+```yaml
+# config/packages/varnish.yaml
+
+shopware:
+    http_cache:
+        reverse_proxy:
+            enabled: true
+            use_varnish_xkey: true
+            hosts:
+                # address to this varnish container or all varnish containers
+                - localhost:6081
+```
+
+</details>
+
+<details>
+  <summary>Config for Shopware 6.4 or 6.5</summary>
+
+```yaml
+# config/packages/varnish.yaml
+
+storefront:
+    reverse_proxy:
+        enabled: true
+        use_varnish_xkey: true
+        hosts:
+            # address to this varnish container or all varnish containers
+            - localhost:6081
+```
+
+</details>
 
-- `SHOPWARE_BACKEND_HOST` - The host of the Shopware backend. Default: `localhost`
-- `SHOPWARE_BACKEND_PORT` - The port of the Shopware backend. Default: `8000`
-- `SHOPWARE_SOFT_PURGE` - If set to `1`, the soft purge feature is enabled. Default: `0`
 
 ## Example usage
 
@@ -17,6 +48,15 @@ docker run \
     # host ip where Shopware is
     -e SHOPWARE_BACKEND_HOST=host.docker.internal \
     -p 8080:80 \
-    --name=varnish \
-    varnish
+    ghcr.io/shopwarelabs/varnish:latest
 ```
+
+## Additional environment variables
+
+- `SHOPWARE_BACKEND_HOST` - The host of the Shopware backend. Default: `localhost`
+- `SHOPWARE_BACKEND_PORT` - The port of the Shopware backend. Default: `8000`
+- `SHOPWARE_SOFT_PURGE` - If set to `1`, the soft purge feature is enabled. Default: `0`
+
+## Further information
+
+As this image bases on the Official Varnish image, you can use all options available there. For more information, please visit the [official Varnish image documentation](https://hub.docker.com/_/varnish).