Document built-in resources

Summary of the new feature / enhancement

As a user, I want to be able to review reference documentation for the built-in resources provided with DSC instead of needing to review example configurations, the resource manifests, and GitHub work items to understand how to use those resources.

Proposed technical implementation details (optional)

Draft the documentation for the following resources in the docs/reference folder before syncing to the online documentation:

• Resource reference overview
• DSC.PackageManagement/Apt
• DSC.PackageManagement/Brew
• Microsoft/OSInfo
• Microsoft.DSC/Assertion
• Microsoft.DSC/Group
• Microsoft.DSC/Include
• Microsoft.DSC/PowerShell
• Microsoft.DSC.Debug/Echo
• Microsoft.DSC.Transitional/RunCommandOnSet
• Microsoft.Windows/RebootPending
• Microsoft.Windows.OpenSSH.SSHD/sshd_config
• Microsoft.Windows/WMI
• Microsoft.Windows/WindowsPowerShell

Start in the docs/reference folder and review the checked resource pages alongside the unchecked resource list in the issue. Use the existing example configurations, resource manifests, and linked work items as reference for each remaining built-in resource. Done means the unchecked resources have reference documentation drafted and the documentation is ready to sync online.