Add GH actions example

[eduherminio]

Add example workflow file with one job:

• Builds the solution
• Publishes the engine as self-contained, trimmed, single-file executable
• Uploads the resulting artifact

And it does that for each environment ([ubuntu-latest, windows-latest, macOS-latest, macos-14]) You can see the result (running in my fork) here. At the bottom you get the artifacts generated by it.

If you implement a command that does some search and exists without human intervention, you could add it that after the publish and double check that it executes correctly in that runner.

Feel free to have a look at my own ones, especially CI and release ones could be useful.