Generate C API diff using GMLC-TDC/cheader2json

[nightlark]

After the release builds for a new release have finished, trigger a new workflow that uses https://github.com/GMLC-TDC/cheader2json (available on PyPI as cheader2json) to generate a JSON file with a diff of the functions that have changed in the HELICS C API between the last release and the current release.

The generate-diff action (https://github.com/GMLC-TDC/cheader2json/tree/main/actions/generate-diff) might be useful for this. Whether this action is used, or a source tarball from the latest GitHub releases, the header file to diff will be under src/helics/shared_api_library/backup/helics/helics.h