feat(lightrag): Implement mix search mode combining knowledge graph and vector retrieval

- Add 'mix' mode to QueryParam for hybrid search functionality
- Implement mix_kg_vector_query to combine knowledge graph and vector search results
- Update LightRAG class to handle 'mix' mode queries
- Enhance README with examples and explanations for the new mix search mode
- Introduce new prompt structure for generating responses based on combined search results

lightrag/base.py

@@ -16,7 +16,7 @@ T = TypeVar("T")
 
 @dataclass
 class QueryParam:
-    mode: Literal["local", "global", "hybrid", "naive"] = "global"
+    mode: Literal["local", "global", "hybrid", "naive", "mix"] = "global"
     only_need_context: bool = False
     only_need_prompt: bool = False
     response_type: str = "Multiple Paragraphs"