updating BYOS commands to mark them as preview (#11755)

This feature is in preview and this should be indicated

src/azure-cli/azure/cli/command_modules/appservice/commands.py

@@ -121,10 +121,10 @@ def load_command_table(self, _):
         g.custom_command('delete', 'delete_connection_strings')
 
     with self.command_group('webapp config storage-account') as g:
-        g.custom_command('list', 'get_azure_storage_accounts', exception_handler=empty_on_404)
-        g.custom_command('add', 'add_azure_storage_account')
-        g.custom_command('update', 'update_azure_storage_account')
-        g.custom_command('delete', 'delete_azure_storage_accounts')
+        g.custom_command('list', 'get_azure_storage_accounts', exception_handler=empty_on_404, is_preview=True)
+        g.custom_command('add', 'add_azure_storage_account', is_preview=True)
+        g.custom_command('update', 'update_azure_storage_account', is_preview=True)
+        g.custom_command('delete', 'delete_azure_storage_accounts', is_preview=True)
 
     with self.command_group('webapp config hostname') as g:
         g.custom_command('add', 'add_hostname', exception_handler=ex_handler_factory())