feat: add option for filtering read stickied on all discussions page (#4073)

Co-authored-by: Adrian McCay <2762877+adrianmccay@users.noreply.github.com>

extensions/sticky/extend.php

@@ -50,4 +50,8 @@ return [
     (new Extend\SearchDriver(DatabaseSearchDriver::class))
         ->addFilter(DiscussionSearcher::class, StickyFilter::class)
         ->addMutator(DiscussionSearcher::class, PinStickiedDiscussionsToTop::class),
+
+    (new Extend\Settings())
+        ->default('flarum-sticky.only_sticky_unread_discussions', true)
+        ->serializeToForum('onlyStickyUnreadDiscussions', 'flarum-sticky.only_sticky_unread_discussions', 'boolval'),
 ];