feat: allow a flag to not set gitignore on netlify dev

[khendrikse]

🎉 Thanks for submitting a pull request! 🎉

Summary

This adds a flag to the dev command so it does not automatically add the .netlify folder to the gitignore.

---

For us to review and ship your PR efficiently, please perform the following steps:

• Open a bug/issue before writing your code 🧑‍💻. This ensures we can discuss the changes and get feedback from everyone that should be involved. If you`re fixing a typo or something that`s on fire 🔥 (e.g. incident related), you can skip this step.
• Read the contribution guidelines 📖. This ensures your code follows our style guide and
  passes our tests.
• Update or add tests (if any source code was changed or added) 🧪
• Update or add documentation (if features were changed or added) 📝
• Make sure the status checks below are successful ✅

A picture of a cute animal (not mandatory, but encouraged)

[github-actions]

📊 Benchmark results

Comparing with c064e01

• Dependency count: 1,074 (no change)
• Package size: 297 MB (no change)
• Number of ts-expect-error directives: 382 (no change)