{AzureAppService} Mention the syntax format for ConnectionStrings parameter (#21381)

* {AzureAppService} Mention the syntax format for ConnectionStrings parameter

Fixes #21373

This PR mentions the syntax format for ConnectionStrings parameter:
> $connStrings = @{ConnectionStringName = @{ Type = "MySql"; Value = "TestValue"}}

* Update SetAzureWebAppSlot.cs

* Update SetAzureWebAppSlot.cs

Author: navba-MSFT

src/Websites/Websites/Cmdlets/DeploymentSlots/SetAzureWebAppSlot.cs

@@ -65,7 +65,7 @@ public class SetAzureWebAppSlotCmdlet : WebAppSlotBaseCmdlet
         [ValidateNotNullOrEmpty]
         public Hashtable AppSettings { get; set; }
 
-        [Parameter(Position = 11, Mandatory = false, HelpMessage = "Web app connection strings")]
+        [Parameter(Position = 11, Mandatory = false, HelpMessage = "Web app connection strings, Example: $connStrings = @{ConnectionStringName = @{ Type = \"MySql\"; Value = \"TestValue\"}}")]
         [ValidateNotNullOrEmpty]
         public Hashtable ConnectionStrings { get; set; }
 

src/Websites/Websites/help/Set-AzWebAppSlot.md

@@ -180,7 +180,7 @@ Accept wildcard characters: False
 ```
 
 ### -ConnectionStrings
-Connection Strings HashTable
+Connection Strings HashTable. Example: `$connStrings = @{ConnectionStringName = @{ Type = "MySql"; Value = "TestValue"}}`
 
 ```yaml
 Type: System.Collections.Hashtable