make the scripts optional as part of an extra

[DetachHead]

i'm considering switching to this project from nodejs-bin. it makes the node, npm and npx scripts optional and only installs them if you install the cmd extra:

pip install 'nodejs-bin[cmd]'

that's useful in my case because i only need to call node programmatically and not via the command line, and i'd prefer users of my package to not unknowingly have a node binary added to their path.

[njzjz]

We may have two options to do it (like scikit-build/cmake-python-distributions#80 (comment)). One is

• nodejs-wheel[cmd]
• nodejs-wheel

Another one is

• nodejs-wheel
• nodejs-wheel-binaries
  (nodejs-wheel is based on nodejs-wheel-binaries)

I prefer the second one, as it has no breaking change to nodejs-wheel.