Add a CI workflow using GitHub Actions

[SmileyAG]

It would be great to have automatic builds.

And the point is not at all that manual building can be difficult, it’s just that re-building locally for each new version does not seem like a convenient solution.

Here is an example of CI workflow from other Ghidra extension project for reference: https://github.com/chaoticgd/ghidra-emotionengine-reloaded/blob/main/.github/workflows/publish.yml

When there is a CI workflow, it is not difficult to change the following parameters for shipping builds, such as:

• JDK version and distribution
• Gradle version
• Ghidra version