Nx: node: support creating libraries and publishable libraries

[Hotell]

Prerequisites

• [x] I am running the latest version
• [x] I checked the documentation (nx.dev) and found no answer
• [x] I checked to make sure that this issue has not already been filed
• [x] I'm reporting the issue to the correct repository (not related to React, Angular or any dependency)

Expected Behavior

To officially support @nx g @nrwl/node:lib my-node-utils --publishable

We can already generate node library via schematic, although it's not documented (inherited from @nrwl/workspace I assume):

Current Behavior

Currently I can generate node library via @nx g @nrwl/node:lib my-node-utils,
which is missing build builder. I can add it on my own ofc, but it would be much better to add --publishable functionality.

• version of Nx used (_Please run nx report at the root of your workspace and copy the results here if you are using Nx 8.6.1 or greater_): 8.9.0
• 3rd-party libraries and their versions
• and most importantly - a use-case that fails

[tommck]

We should be able to build pure script publishable libraries too.. should be in the "@nrwl/workspace" library schematics too