Applicability to existing projects

[c-martinez]

Checklist before submitting an issue

• I have checked the existing issues and couldn't find an issue about this bug.
  Some issues which may be related: Improve documentation on applying template to an existing codebase #589, Applying the template to existing code with tests creates dummy test files #578, Explain how to migrate an existing cookiecutter project to copier #426, Think of different testing scenarios (e.g. start from scratch, add to existing, update existing, switching a profile) #425

Issue details

During the research software templates session in RSECon24, there were several comments in the mentimeter which related to the possible difficulty and potential benefit of applying the template to existing code bases.

This is something that has been discussed in other issues, but it is good to know that others share this concern.

Mentimeter comments were along the lines:
The template should be used easily on existing projects;
It would be useful for applying specific things to existing projects e.g. adding Github Actions for publication;
ensure it is easy to update to new versions