Repo sync tool: Partial equality checks/merges

[mickmister]

Sometimes we add a new script to the scripts portion of package.json, and we want every plugin to receive this change. This requires a manual reconciliation of changes after overwriting the file (or however you choose to go about it), because each plugin understandably has several dependency differences.

It would be great to be able to have a check for this for the purposes of CI. Something like "are the target plugin's package.json scripts up to date with the starter template's scripts?" Then we know this target repo needs to have an sync update. The action of updating the file would ideally support a partial update as well, only updating the scripts part of the file.