Refa: better gitignore (#5473)

### What problem does this PR solve?

when develop ragflow local there would be a hash file generate that is
kind of not good for develop
this patch add a regex to `.gitignore` for better developing 

### Type of change

- [x] Refactoring

Signed-off-by: yihong0618 <zouzou0208@gmail.com>

.gitignore

@@ -38,3 +38,6 @@ sdk/python/dist/
 sdk/python/ragflow_sdk.egg-info/
 huggingface.co/
 nltk_data/
+
+# Exclude hash-like temporary files like 9b5ad71b2ce5302211f9c61530b329a4922fc6a4
+*[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]*