Add snowpack configuration for the tests

[MangelMaxime]

Description

It would be nice to add snowpack to the tests projects.

In #30, I was not able to configure snowpack because it was complaining about react-native not installed which I don't need for the browser. And if, I tried to install it of course it didn't work.

Depending on how snowpack works, it could be added in its own folder like tests/webpack and tests/parcel or use the tests/index.html file as entry point like Vite.

Adding snowpack would also require to:

1. Add a tests:watch-snowpack to the package.json with a dedicated port
2. Add Snowpack to the bundler list in tests/App.fs and fix the warning/errors.