Compat: add new Creative Mail compat file

[jeherve]

Changes proposed in this Pull Request:

This should facilitate the installation and the configuration of the plugin.
The installation tools in there are to be used in tandem with a JITM, introduced in D48025-code.

Jetpack product discussion

• Internal references:
  • pbtFPC-GX-p2
  • pbtFPC-HO-p2

Does this pull request change what data or activity we track or use?

• No

Testing instructions:

• Apply D48025-code on your WordPress.com sandbox.
• Start on a Jetpack site with this branch checked out.
• The Jetpack site should point to your WordPress.com sandbox, with the JETPACK__SANDBOX_DOMAIN constant.
• I would recommend disabling the cache for JITM messages, with add_filter( 'jetpack_just_in_time_msg_cache', '__return_false' );
• The site must be connected to WordPress.com, and the Contact Form module must be active.
• The Creative Mail plugin should not be active on your site.
  • You can test this diff with both the plugin installed but not active, or not installed at all.
• Go to the Feedback menu in your dashboard.
• Try clicking the CTA in the banner that appears.
• Upon plugin activation, run wp option get CE4WP_REFERRED_BY
• You should see the following data being returned:

array (
  'plugin' => 'jetpack',
  'version' => '8.9-alpha',
  'time' => 1597304061,
  'source' => 'jitm',
)

Proposed changelog entry for your changes:

• Compatibility: add new Creative Mail compatiblity file.

[matticbot]

Caution: This PR has changes that must be merged to WordPress.com
Hello jeherve! These changes need to be synced to WordPress.com - If you 're an a11n, please commandeer and confirm D48026-code works as expected before merging this PR. Once this PR is merged, please commit the changes to WP.com. Thank you!
This revision will be updated with each commit to this PR

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

E2E results is available here (for debugging purposes): https://jetpack-e2e-dashboard.herokuapp.com/pr-16818

Scheduled Jetpack release: September 1, 2020.
Scheduled code freeze: August 25, 2020

Generated by 🚫 dangerJS against 153c5b8

[sergeymitr]

Works as a charm 🚢

[jeherve]

r212216-wpcom