Bring back executables for subscripts

[stucka]

Work to use a newer version of Python in #34 appears to have ended the ability to get a scripted installed for warn-scraper, warn-transformer and warn-bot. I'm guessing this is a packaging problem involving the newer setuptools format and pyproject.toml, but I don't see where it was getting created in earlier versions either, e.g.,

pipenv install warn-transformer==1.3.303

gets me an executable but pipenv install warn-transformer will not.

[stucka]

Via the kind @eyeseast , this appears to be the solution

https://packaging.python.org/en/latest/guides/creating-command-line-tools/