jan/feature/20260617-py-mod-mk-support-py-init-submodules into master Add support for PY_INIT_SUBMODULES to py-mod.mk. If it is defined in a Makefile including py-mod.mk, the listed submodules will be added to __init__.py and thus included in the list of things that can be imported from a module. This commit also adds support for --submodules to python-tools.sh for that to happen. Signed-off-by: Jan Lindemann <jan@janware.com>