update README

README.md

 # PaddleOCR
 ## 论文
 det、rec、cls三个模型的backbone基于mobilenetv3，可参考mobilenetv3的相关论文
+
 https://arxiv.org/pdf/1905.02244.pdf
 ## 模型结构
 
 det:
-Backbone:
-  name: MobileNetV3
-  scale: 0.5
-  model_name: large
-Neck:
-  name: DBFPN
-  out_channels: 256
-Head:
-  name: DBHead
+  └─ Backbone:
+      └─ name: MobileNetV3
+      └─ scale: 0.5
+      └─ model_name: large
+  └─ Neck:
+      └─ name: DBFPN
+      └─ out_channels: 256
+  └─ Head:
+      └─ name: DBHead
 
 rec:
-Backbone:
-  name: MobileNetV1Enhance
-  scale: 0.5
-  last_conv_stride: [1, 2]
-  last_pool_type: avg
-Head:
-  name: MultiHead
-  head_list:
-    - CTCHead:
-        Neck:
-          name: svtr
-          dims: 64
-          depth: 2
-          hidden_dims: 120
-          use_guide: True
-        Head:
-          fc_decay: 0.00001
-    - SARHead:
-        enc_dim: 512
-        max_text_length: *max_text_length
+  └─ Backbone:
+      └─ name: MobileNetV1Enhance
+      └─ scale: 0.5
+      └─ last_conv_stride: [1, 2]
+      └─ last_pool_type: avg
+  └─ Head:
+      └─ name: MultiHead
+      └─ head_list:
+        └─ CTCHead:
+            └─ Neck:
+              └─ name: svtr
+              └─ dims: 64
+              └─ depth: 2
+              └─ hidden_dims: 120
+              └─ use_guide: True
+            └─ Head:
+              └─ fc_decay: 0.00001
+        └─ SARHead:
+            └─ enc_dim: 512
+            └─ max_text_length: *max_text_length
 
 cls:
-Backbone:
-  name: MobileNetV3
-  scale: 0.35
-  model_name: small
-Head:
-  name: ClsHead
-  class_dim: 2
+  └─ Backbone:
+      └─ name: MobileNetV3
+      └─ scale: 0.35
+      └─ model_name: small
+  └─ Head:
+      └─ name: ClsHead
+      └─ class_dim: 2
 ## 算法原理
 det->cls->rec->text
 ## 数据集