feat: support json file (#1217)

### What problem does this PR solve?

feat: support json file.

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [x] New Feature (non-breaking change which adds functionality)

---------

Co-authored-by: KevinHuSh <kevinhu.sh@gmail.com>

rag/nlp/__init__.py

@@ -471,7 +471,9 @@ def naive_merge(sections, chunk_token_num=128, delimiter="\n。；！？"):
         tnum = num_tokens_from_string(t)
         if tnum < 8:
             pos = ""
+        # Ensure that the length of the merged chunk does not exceed chunk_token_num  
         if tk_nums[-1] > chunk_token_num:
+
             if t.find(pos) < 0:
                 t += pos
             cks.append(t)