Specify or document a way to retrieve softwareVersion from elsewhere

[christophehenry]

Project version is often already specified in somewhere in a a project file. For python projects, for instance, it may be setup.py, setup.cfg, pyproject.toml or version.py. The pyproject.toml standard, offers the attr: package.__version__ syntax for sourcing from a python file.

publiccodeyml should offer a similar feature. softwareVersion could be extended to be used like this:

softwareVersion:
  file: pyproject.toml
  search: 'version\s+=\s+"(?P<version>[^"]+)"'

Maybe something simpler that regexes can be found, IDK.