Add Powershell language file
I noticed there is no powershell language file in gtksourceview.
PowerShell is a task automation and configuration management framework from Microsoft, consisting of a command-line shell and associated scripting language. It was made open-source and cross-platform on 18 August 2016.
The project cherrytree has a powershell.lang
file under GPLv3: https://github.com/giuspen/cherrytree/blob/master/language-specs/powershell.lang
Maybe it could be included in gtksourceview?