Feature: Adds new CLI parameter entrypoint

[paolorechia]

Implements suggestion from this issue: #11

The commits are rather dirty, please let me know if I should squash them.

I only tested locally with Python 3.10 with the following parameters (using pip install -e .)

ptw .
ptw . --now
ptw . --now --entrypoint tox
ptw . --entrypoint tox

[paolorechia]

Thanks for the quick review!

I will do the changes when I get some free time over the next days.

If you prefer to revert the dataclass decorator I can do that as well, I was not aware it wasn’t available in Python 3.6.

[paolorechia]

@olzhasar I've made the requested changes and dropped support for py36 in tox.ini, please double check

I've tested with these

 ptw . 
 ptw . --now
 ptw . --runner tox
 ptw . --now --runner tox -v

[olzhasar]

@paolorechia
I've made some minor changes for clarity
Overall, looks good to me!
Feel free to merge it

Thanks for the contribution!

[paolorechia]

@olzhasar Thanks again for reviewing! Happy to contribute.

I don't think I have permission to merge this PR, would you mind doing it?

I also forgot to ask before, but I guess we should bump the version and release a new package.

[olzhasar]

@paolorechia
That's strange, I'll check permissions.
Yes, I'll release a new version soon, probably tommorow