Setup

# cria um projeto sem aplicativo;
ng new hello-angular-lib --create-application=false
# cria a biblioteca '@pvv/hello-lib'
ng g library @pvv/hello-lib
# criar um componente para a biblioteca:
ng g c button
# buildar o projeto
ng build --prod
# entrar na pasta 'dist'
cd dist/<arquivos.do.projeto>
# logar no npm (é necessário criar uma conta)
npm login
# publicar a biblioteca
#
#   ps: pacotes com '@' no início são pacotes privados # e o NPM cobra!
#

npm publish --access public

BugFix

Erro:

npm ERR! code E426
npm ERR! 426 Upgrade Required - PUT http://registry.npmjs.org/formats_date

npm ERR! A complete log of this run can be found in:
npm ERR!     C:\Users\Administrator\AppData\Local\npm-cache\_logs\2021-11-25T06_55_02_155Z-debug.log
error Command failed with exit code 1.

Digite:

npm config set registry=https://registry.npmjs.org
# fonte: https://debugah.com/npm-contracting-error-e426-22730/