NPM Package Fails to Install on Mingw

[nathaniel-daniel]

🐛 Bug description

The npm package fails to install on mingw:

npm ERR!   throw new Error(`Unsupported platform: ${type} ${arch}`);
npm ERR!   ^
npm ERR!
npm ERR! Error: Unsupported platform: MINGW32_NT-10.0 x64

This is due to the script not detecting the Windows environment correctly. I have a branch at https://github.com/nathaniel-daniel/wasm-pack/tree/mingw that fixes the issue, which I can turn into a PR.

🤔 Expected Behavior

The package should have installed.

👟 Steps to reproduce

1. Install msys2.
2. Enter the ucrt64 env (ucrt64)
3. Install nodejs (pacman -S ucrt64/mingw-w64-ucrt-x86_64-nodejs)
4. Create a new project with wasm-pack as a dependency or dev dependency.
5. Run npm i

🌍 Your environment

Include the relevant details of your environment.
wasm-pack version: N/A (Issue with NPM package)
rustc version: N/A (Issue with NPM package)