Add links to the two examples (dottxt-ai#1062)

Add links to the two examples:
- Q&A with Citations
- Knowledge Graph Generation

docs/cookbook/index.md

@@ -6,3 +6,5 @@
 - [Chain Of Density](chain_of_density.md): Summarize documents using chain of density prompting and JSON-structured generation.
 - [Playing Chess](models_playing_chess.md): Make Mistral-7B play chess against itself using regex-structured generation.
 - [SimToM](simtom.md): Improve LLMs' Theory of Mind capabilities with perspective-taking prompting and JSON-structured generation.
+- [Q&A with Citations](qa-with-citations.md): Answer questions and provide citations using JSON-structured generation.
+- [Knowledge Graph Generation](knowledge_graph_extraction.md): Generate a Knowledge Graph from unstructured text using JSON-structured generation.