Exclude - and $ from PowerShell wordSeparators

[andyleejordan]

This is only a supplied default, so users can easily override it.

This suggestion came from a "Getting Started with VS Code for PowerShell" presentation by @FriedrichWeinmann, thanks!

[jhoneill]

This is mentioned in the release notes for the latest extension, it's the right default (I prefer the non default behaviour)

What I found frustrating is the terminal window has its own behaviour. Extensions shouldn't change this (because each one might change it a different way) but if the release notes mentioned that Terminal › Integrated: Word Separators in settings may be set to match what have for your editor that would save other people hunting for it.