Add support to an attribute in README that can force adding "-AsJob" in generated cmdlets

Currently -AsJob is only generated for long running operations, but sometimes -AsJob is also required for sync api calls. An attribute in the readme file should be added to force creating -AsJob when auto generating cmdlets, so that those which are not long running operations can also have the parameter.

A user scenario:
A customer might run Get-AzStorageAccount parallelly on many test machines, and sometimes the cmdlet will run for a long time since the server's busy. And the customer doesn't want to wait for too long on it, and want to just make the cmdlet fail.