add tag in python.md (#13601)

Co-authored-by: Yan Zhang (WICRESOFT NORTH AMERICA LTD) <[email protected]>

specification/compute/resource-manager/readme.python.md

@@ -35,6 +35,7 @@ Generate all API versions currently shipped for this package
 ```yaml $(multiapi)
 clear-output-folder: true
 batch:
+  - tag: package-2021-03-01
   - tag: package-2020-12-01-only
   - tag: package-2020-10-01-preview-only
   - tag: package-2020-09-30-only
@@ -65,6 +66,16 @@ clear-output-folder: false
 perform-load: false
 ```
 
+### Tag: package-2021-03-01
+
+These settings apply only when `--tag=package-2021-03-01 --python` is specified on the command line.
+Please also specify `--python-sdks-folder=<path to the root directory of your azure-sdk-for-python clone>`.
+
+``` yaml $(tag) == 'package-2021-03-01'
+namespace: azure.mgmt.compute.v2021_03_01
+output-folder: $(python-sdks-folder)/compute/azure-mgmt-compute/azure/mgmt/compute/v2021_03_01
+```
+
 ### Tag: package-2020-12-01-only and python
 
 These settings apply only when `--tag=package-2020-12-01-only --python` is specified on the command line.