Chore: add cookiecutter.json and fix license coverage

[stevenhua0320]

@sbillinge Ready to review

[sbillinge]

Thanks @stevenhua0320 very clean PR!

[stevenhua0320]

@sbillinge I think we have finished this package's recutting, we can safely merge migration to main branch. We should copy the release issue template created by Zhiming @zmx27 to here and start the release preparation process.
Till now the pytest on local looks like this

(diffpy.srxplanar-env) ~/dbs/diffpy.srxplanar/diffpy.srxplanar git:[migration]
pytest
===================================================================== test session starts ======================================================================
platform darwin -- Python 3.13.9, pytest-8.4.2, pluggy-1.6.0
rootdir: /Users/huarundong/dbs/diffpy.srxplanar/diffpy.srxplanar
configfile: pyproject.toml
plugins: env-1.2.0, cov-7.0.0
collected 1 item                                                                                                                                               

tests/test_version.py .                                                                                                                                  [100%]

====================================================================== 1 passed in 0.03s =======================================================================

The git status is also clean now:

(diffpy.srxplanar-env) ~/dbs/diffpy.srxplanar/diffpy.srxplanar git:[migration]
git status
On branch migration
Your branch is ahead of 'origin/migration' by 3 commits.
  (use "git push" to publish your local commits)

nothing to commit, working tree clean