Design and implement strategy for releasing extensions via GitHub actions

[prodonjs]

• Investigate the optimal path for creating releases which allows each extension to be released independently of one another.
• Determine the best solution to automate pushes to NPM and PyPi for shared package
  • https://www.npmjs.com/package/gcp_jupyterlab_shared
  • https://github.com/marketplace/actions/npm-publish
  • https://pypi.org/project/gcp-jupyterlab-shared/
  • https://github.com/marketplace/actions/pypi-publish
• Implement a solution using GitHub actions to be be run on pushes to tags and/or branches.
  • https://github.com/marketplace/actions/create-a-release

[prodonjs]

First steps are to collect the Python tarballs for each package into build artifacts. This will make it possible to get the reproducible build artifacts from a particular commit in the master branch.

For now, the initial strategy can be to manually create a release with a particular extension's tarball.

See example output at: https://github.com/prodonjs/jupyter-gcs-contents-manager/actions/runs/167869896