feat(spotlight): add support for custom search-engines (#1200)

* feat(spotlight): add search settings link

* feat(search-engine): add to manage pages

* feat(spotlight): add children option for external search engines

* chore: revert search settings

* fix: deepsource issue

* fix: inconsistent breadcrum placement

* chore: address pull request feedback

packages/db/migrations/sqlite/0008_third_thor.sql

@@ -0,0 +1,8 @@
+CREATE TABLE `search_engine` (
+	`id` text PRIMARY KEY NOT NULL,
+	`icon_url` text NOT NULL,
+	`name` text NOT NULL,
+	`short` text NOT NULL,
+	`description` text,
+	`url_template` text NOT NULL
+);