workflow: add a github action to auto build plugins.json

Developers make pr changing their own package directory, but usually they don't run script.

Can we introduce Github action to refine this workflow? Because any changes to the package director will not work until the script get executed.

Locate the script that builds plugins.json and inspect how package-directory changes are currently handled. Then review the repository's existing workflow configuration, if any, and define completion as a GitHub Action that runs the script when relevant package files change and keeps plugins.json updated.

Written by the indexing model from the issue text.