Add command line support using scripts/generate.py

[OverkillGuy]

Ship a poetry script (package-exported executable command) from the
scripts/generate.py file.

Refactor the main into a function for entrypoint purposes.

Ref #131

[OverkillGuy]

Note that I do not know how the generate.py script is supposed to work, I just repackaged it to binary for now. I can only execute that generate function from diagrams command right now, but didn't yet run it successfully.

Marked PR as draft until that's understood.

[OverkillGuy]

Hmm on second thought, my drive-by contribution might be ill conceived, my apologies.
I thought the generate.py file was meant as a CLI shortcut to render images, seems it's not meant for that at all.

I still believe exposing a binary command is valuable in general, and the side effect of allowing pipx installation without a python project sounds great too?

[mingrammer]

Ye, the generate.py is not for generating the diagrams. It is used for generating the node classes for the diagrams library.

I saw the issue you created: #131. I'll review that feature positively :)

Thank you!