docs: add YAML example to PromptBuilder documentation

docs-website/docs/pipeline-components/builders/promptbuilder.mdx

@@ -257,6 +257,45 @@ p.run(
 Note that `language_template` introduces `answer_language` variable which is not bound to any pipeline variable. If not set otherwise, it would use its default value, "English". In this example, we overwrite its value to "German".
 The `template_variables` allows you to overwrite pipeline variables (such as documents) as well.
 
+### In YAML
+
+This is the YAML representation of the RAG pipeline shown above. It renders a custom prompt template by filling it with the contents of retrieved documents and a query, then sends the rendered prompt to a generator.
+
+```yaml
+components:
+  llm:
+    init_parameters:
+      api_base_url: null
+      api_key:
+        env_vars:
+        - OPENAI_API_KEY
+        strict: true
+        type: env_var
+      generation_kwargs: {}
+      http_client_kwargs: null
+      max_retries: null
+      model: gpt-5-mini
+      organization: null
+      streaming_callback: null
+      system_prompt: null
+      timeout: null
+    type: haystack.components.generators.openai.OpenAIGenerator
+  prompt_builder:
+    init_parameters:
+      required_variables: null
+      template: "\n    Given these documents, answer the question.\\nDocuments:\n\
+        \    {% for doc in documents %}\n        {{ doc.content }}\n    {% endfor\
+        \ %}\n\n    \\nQuestion: {{query}}\n    \\nAnswer:\n    "
+      variables: null
+    type: haystack.components.builders.prompt_builder.PromptBuilder
+connection_type_validation: true
+connections:
+- receiver: llm.prompt
+  sender: prompt_builder.prompt
+max_runs_per_component: 100
+metadata: {}
+```
+
 ## Additional References
 
 🧑‍🍳 Cookbooks: