Mention usage in README

[FranklinYu]

The README did not provide any information for package user. I have searched around, even looking into the doc folder without understanding anything, until I see the template directory with very useful information.

It would be cool if this template is mentioned in README so user can get started in 10 seconds. Typically README is for library consumers (developer writing PowerShell modules); sections like "Building PowerShell Standard Libraries" should in fact go into CONTRIBUTING.md or at lease grouped under "Contributing" section.

Alternatively we can link to this awesome documentation.