Support For Non-AMP Requests

[jeffersonrabb]

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:

This PR registers and enqueues the AMP scripts so that they will be loaded in non-AMP requests, even if the AMP plugin is not installed.

How to test the changes in this Pull Request:

1. Create a Pop-Up, in an incognito window verify that it reveals and behaves normally in an AMP request.
2. Switch AMP mode to Transitional, test that behavior is identical in AMP and non-AMP requests.
3. Do the same in Reader Mode.
4. Disable the AMP plugin, then re-test a page. It should behave just like the AMP version.

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?

[claudiulodro]

Looks good; works good. 👍