Update data_annotation_en.md

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 # DATA ANNOTATION TOOLS
-
 There are the commonly used data annotation tools, which will be continuously updated. Welcome to contribute tools~
 
-## 1. labelImg
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-* Tool description: Rectangular label
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-* Tool address:  https://github.com/tzutalin/labelImg
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-* Sketch diagram:
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-  ![labelimg](../datasets/labelimg.jpg)
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-
-
-## 2. roLabelImg
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-* Tool description: Label tool rewritten based on labelImg, supporting rotating rectangular label
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-* Tool address:   https://github.com/cgvict/roLabelImg
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-* Sketch diagram:![roLabelImg](../datasets/roLabelImg.png)
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-
-
-## 3. labelme
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-* Tool description: Support four points, polygons, circles and other labels
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-* Tool address:   https://github.com/wkentaro/labelme
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-* Sketch diagram:
-
-  ![labelme](../datasets/labelme.jpg)
+### 1. labelImg
+- Tool description: Rectangular label
+- Tool address:  https://github.com/tzutalin/labelImg
+- Sketch diagram:  
+![labelimg](../datasets/labelimg.jpg)
+
+### 2. roLabelImg
+- Tool description: Label tool rewritten based on labelImg, supporting rotating rectangular label
+- Tool address:   https://github.com/cgvict/roLabelImg
+- Sketch diagram:  
+![roLabelImg](../datasets/roLabelImg.png)
+
+### 3. labelme
+- Tool description: Support four points, polygons, circles and other labels
+- Tool address:   https://github.com/wkentaro/labelme
+- Sketch diagram:  
+![labelme](../datasets/labelme.jpg)