Add a test script which is to calculate storage container billable size.

[EmmaZhu]

Description

Checklist

• I have read the Submitting Changes section of CONTRIBUTING.md
• The title of the PR is clear and informative
• The appropriate change log has been updated -- No product change introduced.
• The PR does not introduce breaking changes
• If applicable, the changes made in the PR have proper test coverage
• For public API changes to cmdlets -- No API changes:
  • [N/A]the changes have gone through a cmdlet design review (Microsoft internal partners only)
  • [N/A] the cmdlet markdown files were generated using the platyPS module

[cormacpayne]

@EmmaZhu a couple of small comments. Out of curiosity, what is the intended usage of this script?

[cormacpayne]

@EmmaZhu do you have any objection to using the following link instead?

https://docs.microsoft.com/en-us/powershell/azure/install-azurerm-ps

[EmmaZhu]

Thanks for your comments. Changed and tested module installing and checking as the suggestions.

[EmmaZhu]

To answer the above question"Out of curiosity, what is the intended usage of this script?", seems I cannot reply to it directly:
The script will be a sample for Azure Storage customers to reference to, to get billable size of an Azure Storage container. We will have an article to introduce it.