DEV: Merge topic list card component (#17)

This PR merges the topic-list-item card component into the nextgen theme.

Also does the following cleanup:

* Use template-only ember components
* Use `fire` instead of deprecated `fa-fire` icon
* Lower version requirement for node to 18 to match core
* Add english locale strings for topic status column
* Remove dummy theme settings

---------

Co-authored-by: Martin Brennan <martin@discourse.org>

about.json

@@ -8,7 +8,9 @@
   "minimum_discourse_version": null,
   "maximum_discourse_version": null,
   "assets": {},
-  "modifiers": {},
+  "modifiers": {
+    "svg_icons": ["fire"]
+  },
   "components": [
     "https://github.com/discourse/discourse-sidebar-new-topic-button.git",
     "https://github.com/discourse/discourse-search-banner.git",