Check restricted plugin header fields

[ernilambar]

Fixes #669

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: ernilambar <[email protected]>
Co-authored-by: davidperezgar <[email protected]>
Co-authored-by: swissspidy <[email protected]>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[ernilambar]

@swissspidy Since we are now using get_file_data() for fetching headers, we could also validate Network field which we postponed earlier. I will do it in follow up PR.

[davidperezgar]

Thanks Nilambar for being fast to solve this meta's request.