I was a bit surprised it wasn't already there. I think adding the Intellisense features for DSC in the PowerShell extension would be a great addition.
Example:
File "SomeFile"
{
# <ctrl+space> here shows a list of available options for the File DSC
}
or
File "SomeFile"
{
Ensure = #<ctrl+space> here shows intellisense options of Absent or Present
}
Gene