Fix the WordPress Playground integration

[dkotter]

Description of the Change

We recently had a report that the WordPress Playground instance we use for demo purposes was no longer working. In testing, it was installing Distributor properly but was failing when trying to network-activate the plugin. It seems the issue is related to the deprecation of github-proxy.com that we use to download Distributor, as the final slug that is now downloaded is different (https-github.com-10up-distributor-stable vs distributor-stable).

This PR fixes that and in addition, moves away from using github-proxy.com and now uses the new git:directory resource to avoid any deprecation notices.

How to test the Change

Can load the Playground environment and ensure it works properly by using the following link:

Playground

Changelog Entry

Fixed - Ensure our WordPress Playground integration works properly without any deprecation warnings

Credits

Props @ianfs-com, @dkotter

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added Critical Flows, Test Cases, and/or End-to-End Tests to cover my change.
• All new and existing tests pass.