RerankFinetuning Sample Guide Needs to be written

[chickenrae]

Example can be found here: https://github.com/opea-project/GenAIExamples/tree/main/RerankFinetuning

Documentation should follow this format: https://github.com/opea-project/docs/tree/main/examples/ChatQnA

When draft is complete please place in this folder: https://github.com/opea-project/docs/tree/main/examples

Documentation Guidelines: https://github.com/opea-project/docs/blob/main/developer-guides/doc_guidelines.rst