Add release workflow GitHub Action

[krassowski]

The current manual releases take too much time and lead to mistakes. Let's automate this with a GitHub Action workflow.

A possible underlying issue of the republish I had to do seems to be a glitch of the watch build script. I previously relied on it rebuilding after branch switch but it seems to have stopped picking up changes and wrongly suggesting me that I have the lib up to date. Manual jlpm build(without watch) works though.

Two options:

• manual release on GitHub as a trigger: https://docs.github.com/en/actions/reference/events-that-trigger-workflows
• push to v* branch as a trigger: https://github.com/actions/create-release

This will probably be postponed until after the move to new project organization.

[krassowski]

Closing in favour of #691