GitHub Actions pipeline setup

[radu-stefan-dt]

Summary
The project currently has 1 workflow for building and running the tests on every push or merge into main - this is fine.
The project also has 1 workflow for building across all possible platforms (to support remote envs) and also publish all packages to the marketplace - this needs modifying.

Details
The current workflow for building should first create a GitHub release, attaching as assets all the different platform distributions created from the existing build step.
Publish to marketplace should be a separate (on-demand) workflow that takes the latest release, and publishes an update to the marketplace using the released assets.

Reasoning
We may want to create releases more frequently (bleeding edge), and publish stable versions as/when needed to the marketplace.