feat: adds support for Safety Net plugin

[gamebits]

All Submissions:

• Have you followed the Newspack Contributing guideline?
• Does your code follow the WordPress' coding standards and VIP Go 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 Team 51's Safety Net to our list of supported plugins.

How to test the changes in this Pull Request:

1. Switch to this branch.
2. Install the Safety Net plugin.
3. Go to Newspack > Health Check and confirm that Safety Net is not raising any alerts.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully ran tests with your changes locally?

[matticbot]

🎉 This PR is included in version 2.13.0-alpha.1 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀

[matticbot]

🎉 This PR is included in version 2.13.0 🎉

The release is available on GitHub release

Your semantic-release bot 📦🚀