Add batch tag imagebuilder package-2021-10 (Azure#17018)

Author: Alancere

specification/imagebuilder/resource-manager/readme.go.md

@@ -12,12 +12,22 @@ These settings apply only when `--go` is specified on the command line.
 
 ``` yaml $(go) && $(multiapi)
 batch:
+  - tag: package-2021-10
   - tag: package-2020-02
   - tag: package-2018-02
   - tag: package-2019-02
   - tag: package-preview-2019-05
 ```
 
+### Tag: package-2021-10
+
+These settings apply only when `--tag=package-2021-10 --go` is specified on the command line.
+Please also specify `--go-sdk-folder=<path to the root directory of your azure-sdk-for-go clone>`.
+
+``` yaml $(tag) == 'package-2021-10' && $(go)
+output-folder: $(go-sdk-folder)/services/$(namespace)/mgmt/2021-10-01/$(namespace)
+```
+
 ### Tag: package-2020-02
 
 These settings apply only when `--tag=package-2020-02 --go` is specified on the command line.