feat: allow scikit-package-systemto automatically create the project-level cookiecutter.json.

[ycexiao]

What problem does this PR address?

Closes #30.

What should the reviewer(s) do?

Please check the modifications.

• This PR introduces a public-facing change (e.g., figures, CLI input/output, API).
  • Documentation (e.g., tutorials, examples, README) has been updated.
  • A tracking issue or plan to update documentation exists.
• This PR affects internal functionality only (no user-facing change).

[ycexiao]

@sbillinge @sbillinge, it's ready for review.

[sbillinge]

LGTM. I guess there are no typo's and it works correctly? Pleaes could you show screenshots of an example first time through (default defaults) and second time through (project defaults) and that it doesn't crash or anything bad happen second time through? Then I can merge.

[ycexiao]

@sbillinge
Running package create system in a directory without cookiecutter.json

Change the path to a-different-package-name. cookiecutter.json is created. package create system uses the new default values in the directory

[bobleesj]

@ycexiao Looks good to me!