Assuming powershell is in you PATH you can call it like this:
"scripts": {
"test": "@powershell -NoProfile -ExecutionPolicy Unrestricted -Command ./test.ps1"
}
Tested on Windows 7 with Powershell v4.
Limitations are that you need Powershell installed and in your PATH. I didn’t test it with Powershell for Linux, so not sure if this solution will be portable to other platform for now.