create doc (Azure#24419)

Author: BigCat20196

doc/dev/how_to_request_a_feature_in_sdk.md

@@ -0,0 +1,26 @@
+How to Request a Feature in SDK
+======
+
+This article aims to provide a guide for customers to request a feature in Azure Python SDK.
+
+Python SDK is automatically generated based on rest API, so we generally do not recommend modifying SDK code manually. If you need a new function, but the SDK does not provide it, you need to open an issue in the [rest API](https://github.com/Azure/azure-rest-api-specs/issues) to describe clearly the feature you want.
+
+Then, if the feature is adopted by the service team and the relevant rest API is updated, we will regenerate the SDK and release it after approved.
+
+
+The overall workflow is:
+1. Swagger and service ready
+2. Azure Python SDK release (PyPI)
+
+
+```
+ ---------      ------------ 
+|         |    |            | 
+| Service | -> | Python SDK | 
+|         |    |            |  
+ ---------      ------------
+```
+
+This is the way that Azure Python SDK works with the Service team. Swagger PR should be merged before requesting azure Python SDK support.
+
+Feel free to contact Azure CLI team at any time through any channels. We are passionate to build the world-class cloud product.