pkg.run_script(script, wait=False) does not work

Package version (if known):

## Describe the bug
json file:
```
{
"name": "bookings",
"version": "1.0.0",
"description": "bookings",
"main": "./bookings.js",
"scripts": {
"bookings": "webpack --entry ./bookings.js --output-path . --output-filename bookings.min.js --progress --mode=production --devtool source-map",
"all": "run-p bookings"
},
"author": "Ewald Harmsen",
"license": "ISC",
"devDependencies": {
"webpack": "^5.69.1",
"webpack-cli": "^4.9.2"
}
}

```

I run this on a windows 11 machine

## Steps to Reproduce
1. `pkg = NPMPackage(f'{js_folder}/package.json', shell=True)`
2. `p = pkg.run_script('all', wait=False)`
3. Observe that the script is not run, `p => `

## Expected behavior
should work and run the script

## Screenshots (if applicable)

## Additional context

Start at the NPMPackage.run_script entry point and reproduce the supplied package.json workflow on Windows 11, focusing on the all script with wait=False. Done means the returned process actually launches npm and runs the script asynchronously rather than remaining without the expected execution.

Written by the indexing model from the issue text.