Add PR pipeline artifact to build and publish the plugin ZIP

[erseco]

Add a step to the CI pipeline so that every Pull Request generates a downloadable .zip package of the WordPress plugin.

This would make it easier to test PRs quickly without having to build the plugin manually in a local environment.

Problem

At the moment, reviewing and testing a Pull Request requires checking out the branch and preparing the plugin package manually.

This slows down validation, especially when the goal is just to install the plugin in a WordPress instance and verify the proposed changes.

Proposed solution

Update the pipeline to:

1. Build the plugin package as a .zip file for every Pull Request.
2. Expose that .zip as a pipeline artifact.
3. Make the artifact easy to find and download from the PR-related pipeline job.

Expected behavior

For each PR, reviewers should be able to:

• Open the pipeline
• Download the generated plugin .zip
• Install it directly in WordPress
• Test the PR changes quickly

Notes

• The generated ZIP should contain only the files required for plugin installation.
• Development-only files and folders should be excluded where appropriate.
• The artifact name should be predictable and easy to identify, for example:
  • wp-exelearning-pr-<PR_NUMBER>.zip
  • or wp-exelearning-<BRANCH_NAME>.zip

Benefits

• Faster QA and manual testing
• Easier review workflow for non-developer testers
• Consistent packaging across PRs
• Less time spent preparing test builds manually

Acceptance criteria

• A PR pipeline generates a plugin .zip automatically
• The .zip is available as a downloadable pipeline artifact
• The package can be installed in WordPress without extra preparation
• The artifact is clearly named and tied to the PR build