Enable `test-new-project-works` in CI for Windows

[philpax]

The test-new-project-works GitHub Actions job runs the built Ambient executable on each platform, and uses it to create a new project which it then checks for validity. This lets us test that the built executable is valid for that platform.

Unfortunately, I've had to disable it for Windows because the runner keeps running out of space. This can be solved by either freeing up space in the VM, or by reducing the size of the build. Suggestions and PRs welcome! (If you do test this, you'll probably want to do it on your own fork)

The action in question: https://github.com/AmbientRun/Ambient/blob/a7349ba3c296cc70c8e6c7b98247e2b630f610ea/.github/workflows/ci.yml#L180-L211