Add section to inject custom context via docstring

This update enhances the Jupyter notebook add_context_to_llm_descriptions.ipynb by introducing a new section. This section guides you on embedding explicit instructions within a test's docstring to influence LLM-generated test result descriptions. Titled Add test-specific context using the docstring, it addresses the issue where non-instructional context in docstrings was previously ignored by the LLM. You are now advised to format specific lines as instructions using syntax like: INSTRUCTION: Please add the following note at the end of the description: "NOTE: This is a sample of the data, for the full data results please look in the appendix." This ensures your intended context is reliably included in the LLM-generated descriptions.