Add `.gitignore` to new projects

[jbergstroem]

Clear and concise description of the problem

Improve DX by adding a .gitignore when initializing a project (even if its not managed by git) that at a minimum would contain node_modules and tsp-output.

Checklist

• [X] Follow our Code of Conduct
• [X] Read the docs.
• [X] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[timotheeguerin]

are you suggesting tsp init should be doing that?

[jbergstroem]

are you suggesting tsp init should be doing that?

Yes, as part of setting up a project directory. Sorry if I wasn't clear enough.

[timotheeguerin]

Should be easy enough maybe add as a prompt (Add default .gitignore? Y/n)