Update SDK->sdk, and add create_dataset (#1047)

### What problem does this PR solve?

Add create_dataset method, test for it, and update SDK->sdk.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

Signed-off-by: cecilia-uu <konghui1996@163.com>

.gitignore

@@ -32,7 +32,7 @@ docker/ragflow-logs/
 rag/res/deepdoc
 
 # Exclude sdk generated files
-SDK/python/ragflow.egg-info/
-SDK/python/build/
-SDK/python/dist/
-SDK/python/ragflow_sdk.egg-info/
+sdk/python/ragflow.egg-info/
+sdk/python/build/
+sdk/python/dist/
+sdk/python/ragflow_sdk.egg-info/