✨ Added lazy-loading of comments data (#19778)

no issue

Bumps `Comments-UI` app version that contains a few changes:

- comments data is now lazy-loaded with API requests being deferred until the comments block is scrolled into view, saving up-front visitor data usage as well as reducing server-load for page views where the comments are never seen
- comments data is now fetched from `/members/api/comments/{post_id}/` rather than using the post_id in the `filter` param to enable cache bucketing and cache invalidation
- `created_at` timestamp has been dropped from the initial comments data request so the results can be cached, on pagination requests the timestamp has been improved to use the created_at data from the response so it remains consistent and can also be cached
- `order` param has been dropped from API requests as the API has been updated to include our default ordering

ghost/core/core/shared/config/defaults.json

@@ -195,7 +195,7 @@
     },
     "comments": {
         "url": "https://cdn.jsdelivr.net/ghost/comments-ui@~{version}/umd/comments-ui.min.js",
-        "version": "0.13"
+        "version": "0.15"
     },
     "signupForm": {
         "url": "https://cdn.jsdelivr.net/ghost/signup-form@~{version}/umd/signup-form.min.js",