add profiling model doc (#4694)

* add profiling model doc

* fix doc

* fix

* fix ref

* fix number

* fix

* fix link

* fix format

* fix according to review

* fix according to review

* fix according to review

* fix according to review

* fix according to review

* fix according to review

* fix according to review

* fix

* fix according to review

* fix according to review

* fix according to review

Author: rainyfly

docs/guides/performance_improving/index_cn.rst

@@ -9,4 +9,11 @@
 ..  toctree::
     :hidden:
 
-    quantization.md
+    quantization.md
+
+- `模型性能分析 <./profiling_model.html>`_ : 使用飞桨性能分析器对模型进行性能调试。
+
+..  toctree::
+    :hidden:
+
+    profiling_model.md