We need to extend the command spo group user add with 2 new options

1. groupName
   Currently options only supports specifying groupId as parameter which is the id of the SharePoint group. Now we need to extend the command with groupName so that users can specify SharePoint Group Name as parameter.
   Please note, User can specify either groupId or groupName but not both.

2. email
   Currently options for the command only support userName. But we need to extend the command so that it will even supports email address of the users. Users can even specify multiple email addresses which are comma separated.
   Please note, User can specify either userName or email but not both.

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