Update readme for Synapse management SDK May release (Azure#14054)

* Update readme for Synapse management SDK May release

* Add package-2021-05-preview

* Address comment

Co-authored-by: Dongwei Wang <[email protected]>

Author: idear1203

specification/synapse/resource-manager/readme.md

@@ -28,25 +28,23 @@ These are the global settings for the Azure Synapse Analytics API.
 description: Azure Synapse Analytics Management Client
 openapi-type: arm
 azure-arm: true
-tag: package-preview-2021-04
+tag: package-2021-04-preview
 generate-empty-classes: true
 modelerfour:
   lenient-model-deduplication: true
 ```
 
+### Tag: package-2021-04-preview
 
-### Tag: package-preview-2021-04
+These settings apply only when `--tag=package-2021-04-preview` is specified on the command line.
 
-These settings apply only when `--tag=package-preview-2021-04` is specified on the command line.
-
-``` yaml $(tag) == 'package-preview-2021-04'
+``` yaml $(tag) == 'package-2021-04-preview'
 input-file:
   - Microsoft.Synapse/preview/2021-04-01-preview/bigDataPool.json
   - Microsoft.Synapse/preview/2021-04-01-preview/checkNameAvailability.json
   - Microsoft.Synapse/preview/2021-04-01-preview/firewallRule.json
   - Microsoft.Synapse/preview/2021-04-01-preview/integrationRuntime.json
   - Microsoft.Synapse/preview/2021-04-01-preview/keys.json
-  - Microsoft.Synapse/preview/2021-04-01-preview/kustoPool.json
   - Microsoft.Synapse/preview/2021-04-01-preview/library.json
   - Microsoft.Synapse/preview/2021-04-01-preview/operations.json
   - Microsoft.Synapse/preview/2021-04-01-preview/privateEndpointConnections.json
@@ -57,6 +55,17 @@ input-file:
   - Microsoft.Synapse/preview/2021-04-01-preview/workspace.json
 ```
 
+### Tag: package-kusto-pool-2021-04-preview
+
+These settings apply only when `--tag=package-kusto-pool-2021-04-preview` is specified on the command line.
+
+**ATTENTION**: Please DO NOT generate SDK based on this tag. Kusto pool API set is not ready to be widely used.
+
+``` yaml $(tag) == 'package-kusto-pool-2021-04-preview'
+input-file:
+  - Microsoft.Synapse/preview/2021-04-01-preview/kustoPool.json
+```
+
 ### Tag: package-2021-03
 
 These settings apply only when `--tag=package-2021-03` is specified on the command line.
@@ -262,6 +271,9 @@ csharp:
   namespace: Microsoft.Azure.Management.Synapse
   output-folder: $(csharp-sdks-folder)/synapse/Microsoft.Azure.Management.Synapse/src/Generated
   clear-output-folder: true
+batch:
+ - tag: package-2021-04-preview
+ - tag: package-sqlGen3-2020-04-01-preview
 ```
 
 ## Go