Add *.py extension to all scripts to simplify Windows compatibility

[E3V3A]

Windows still doesn't like files without extensions, and hacking around it with (windows python) shebangs is tricky and not easy for most. Adding wrappers to each script is also too much work.

I will add the extensions to all files.

[wimglenn]

Hey there, @E3V3A this totally breaks the package for Linux and macOS users.

$ pip install -q pip-date
$ pip-date
zsh: command not found: pip-date
$ pip-date.py
zsh: permission denied: pip-date.py

You'll need to set the executable bits on the scripts. But I don't recommend to package scripts like this at all, tbh, it's much better to use the console_scripts entrypoint group of setuptools and just let pip generate the wrappers at install time. I'm not sure what you mean by "too much work", it's just a one-line change in the setup.py pretty much ..