Add plugin row meta

[ipokkel]

Add function plugin_row_meta to class to add doc and support links to plugin row meta.

All Submissions:

• Have you followed the Contributing guideline?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Adds functionality to show plugin documentation and support links.

How to test the changes in this Pull Request:

1. Navigate to Plugins > Installed Plugins
2. Locate the "Paid Memberships Pro - Limit Logins" plugin
3. Verify that the "Docs" and "Support" show and links correctly

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you successfully run tests with your changes locally?

Changelog entry

ENHANCEMENT: Add docs and support links to plugin row meta.