Environment

• Editor and Version: VS Code: 1.26.0
• Your primary theme: Dark+

Issue Description

The subexpression marker(the $ in '$(') is currently scoped in 'punctuation.definition.variable'. This causes no colorization in most schemes, such then cause colorization issues in double quoted text subexpressions.

Expected Behavior

I might think that it should be in a 'keyword' scope. To play around, I modified the VS Code powershell.tmLanguage.json file, in two places, to change the $ in '$(' to be scoped as 'keyword.other.subexpression.powershell'.

This seems to get the result with themes, causing it to colorize the same as the @ in '@(' or '@{' which also scope as a 'keyword'.