Add pipeline YAML example to Haystack documentation page of PromptBuilder

[julian-risch]

We should add a pipeline YAML example to the Haystack documentation page. Should be added right after the example showing how to use the component in a pipeline.

Here are merged PRs for other components as examples:

• Agent: docs: add YAML example for agent pipeline configuration in documentation #11110
• SerperDevWebSearch: docs: Add YAML representation of pipeline for SerperDevWebSearch #11121
• DocumentCleaner: docs: add yaml example to document cleaner documentation #11096

[ritikraj2425]

Hey @julian-risch ,

I came across this issue and would like to work on it. I’ve reviewed the referenced PRs and understand the expected YAML pipeline example format for the documentation.

I’ll start working on the DocumentSplitter update please let me know if there are any specific guidelines I should follow.