Update README

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

README.md

@@ -2,7 +2,7 @@
 
 *author: Kyle He*
 
-
+<br />
 
 ## Desription
 
@@ -23,12 +23,14 @@ where embeddings are learned from a small number of questions and passages by a
 
 [2].https://arxiv.org/abs/2004.04906
 
+<br />
+
 ## Code Example
 
 Use the pretrained model "facebook/dpr-ctx_encoder-single-nq-base"
 to generate a text embedding for the sentence "Hello, world.". 
 
- *Write the pipeline*:
+*Write the pipeline*:
 
 ```python
 from towhee import dc
@@ -39,6 +41,7 @@ dc.stream(["Hello, world."]) \
   .to_list()
 ```
 
+<br />
 
 ## Factory Constructor
 
@@ -48,12 +51,13 @@ Create the operator via the following factory method
 
 **Parameters:**
 
-​	***model_name***: *str*
+***model_name***: *str*
 
-​	The model name in string.
+The model name in string.
 The default value is "facebook/dpr-ctx_encoder-single-nq-base".
 You can get the list of supported model names by calling `get_model_list` from [dpr.py](https://towhee.io/text-embedding/dpr/src/branch/main/dpr.py).
 
+<br />
 
 ## Interface
 
@@ -63,14 +67,13 @@ and then return text embedding in ndarray.
 
 **Parameters:**
 
-​	***text***: *str*
-
-​	The text in string.
+***text***: *str*
 
+The text in string.
 
 
 **Returns**:
 
-​    *numpy.ndarray*
+*numpy.ndarray*
 
-​	The text embedding extracted by model.
+The text embedding extracted by model.