docs: add sync credentials example

readme.md

@@ -10,6 +10,16 @@ Install and configure [Zot](https://zotregistry.dev/) - an OCI-native container
 | `zot_cve_scanning` | No | `false` | Enable CVE scanning of images |
 | `zot_sync_credentials` | No | undefined | List of sync registry credentials (name, registry, username, password) to avoid rate limits |
 
+## Example
+
+```yaml
+zot_sync_credentials:
+  - name: "dockerhub"
+    registry: "registry-1.docker.io"
+    username: "your-dockerhub-username"
+    password: "your-dockerhub-password"
+```
+
 ## Configuration
 
 The role deploys Zot with the following defaults: