Improve: Added Listing Importer and Mailchimp extension descriptions

[RabbiIslamRony]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Security fix
• Improvement
• New Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• Text changes
• Other... Please describe:

Description

How to reproduce the issue or how to test the changes

This fixes the missing Mailchimp Integration description on the Directorist Themes & Extensions subscription list.

The subscription/available-extension flow builds item keys from product permalinks. The current Mailchimp product URL resolves to directorist-mailchimp, while the local extension metadata is stored under directorist-mailchimp-integration. Because there was no alias between those keys, the available subscription row could render the Mailchimp title from subscription data but fail to find the local description from the extension list.

This change adds Mailchimp key aliases so both directorist-mailchimp and directorist-mailchimp-integration resolve to the same extension metadata. It also updates the local Mailchimp product URL/thumbnail reference.

This also adds Directorist Listing Importer to the local fallback extension list with its thumbnail asset, so the extension can be displayed when the remote products API is unavailable or falls back to bundled metadata. The admin plugins list script now normalizes a Listing Importer row from data-slug=listing-importer to data-slug=directorist-listing-importer, so it is grouped with Directorist extensions.

1. Log in to WordPress admin with a Directorist subscription account that includes Mailchimp Integration.
2. Go to Directorist > Themes & Extensions.
3. Find Mailchimp Integration in the available subscription extensions list.
4. Verify the Mailchimp description is displayed instead of an empty description area.
5. Verify the Mailchimp thumbnail still loads correctly.
6. Verify the Install button still targets the Mailchimp subscription item.
7. Optionally refresh the products API/cache and verify the description still resolves when the subscription item key is directorist-mailchimp.
8. Simulate or rely on the local fallback extension list and verify Directorist Listing Importer appears with its description and thumbnail.
9. On the WordPress Plugins page, verify a Listing Importer row with data-slug=listing-importer is normalized/grouped as directorist-listing-importer with the Directorist extensions list.

Any linked issues

Fixes # N/A

Screenshot

• N/A

Checklist

• My code follows the WordPress coding standards