Integration with CI/Automation: dry mode

[AndreaPontrandolfo]

Right now the whole process is manual, but to keep the repos continuously in check we need CI integration.
We need a simple --dry flag.
The flag will simply make npx nolyfill exit the process with exit code 1 (stderr) whenever changes to be made with nolyfill install are found.

Maybe related:

• [Feature Request] Programmatic usage (JavaScript SDK) #20
• public a nolyfill github action ci to auto check other projects #89