Provide a CLI

[di]

What's missing

Right now the https://pypi.org/project/model-signing/ project does not provide a single CLI entrypoint for this library, instead just providing an importable API. The source repo provides sign.py and verify.py scripts, but these are not included in published distributions, and must be used directly from source checkout.

Additionally, the library itself is not executable after install:

$ python -m pip install model_signing
...

$ python -m model_signing
/usr/local/bin/python: No module named model_signing.__main__; 'model_signing' is a package and cannot be directly executed

What I'd like to see

Ideally, upon install, the library provides a CLI with similar functionality to the sign.py and verify.py scripts, e.g.:

$ python -m pip install model_signing
...

$ python -m model_signing --help
usage: model_signing [-h] [-v] [-V] COMMAND ...
model_signing: error: the following arguments are required: COMMAND

$ python -m model_signing sign --help
usage: Script to sign models [-h] --model_path MODEL_PATH [--sig_out SIG_OUT] {pki,private-key,sigstore,skip} ...
Script to sign models: error: the following arguments are required: --model_path, method

$ python -m model_signing verify --help
usage: Script to verify models [-h] --sig_path SIG_PATH [--model_path MODEL_PATH] {pki,private-key,sigstore,skip} ...
Script to verify models: error: the following arguments are required: --sig_path, method

Related
#328 and #329 are related