Update README

Signed-off-by: shiyu22 <shiyu.chen@zilliz.com>

README.md

@@ -16,7 +16,7 @@ Search embedding in [Faiss](https://github.com/facebookresearch/faiss), **please
 
 ## Code Example
 
-- Insert data into Faiss first
+### Insert data into Faiss first
 
 ```python
 import numpy as np
@@ -30,7 +30,7 @@ x = towhee.dc['id'](ids) \
     .to_faiss['id', 'vec'](findex='index.bin')
 ```
 
--  Example
+### Example
 
 *Write the pipeline in simplified style:*
 
@@ -61,11 +61,11 @@ Create the operator via the following factory method:
 
 ***ann-search.faiss(findex)***
 
+<br />
 
 
-**Parameters:**
-
 
+**Parameters:**
 
 ***findex:*** *str* or *faiss.INDEX*
 
@@ -84,6 +84,8 @@ The path to faiss index file or faiss index.
 
 Query embeddings in Faiss
 
+<br />
+
 
 
 **Returns:** *Entity*