DEV: Add keyboard:move selection event (#15241)

allows plugin event hook for keyboard:move-selection. Passes raw selected and all articles through named params.

app/assets/javascripts/discourse/app/lib/keyboard-shortcuts.js

@@ -682,6 +682,10 @@ export default {
     if ($article.length > 0) {
       $articles.removeClass("selected");
       $article.addClass("selected");
+      this.appEvents.trigger("keyboard:move-selection", {
+        articles: $articles.get(),
+        selectedArticle: $article.get(0),
+      });
 
       const articleRect = $article[0].getBoundingClientRect();
       if (!fast && direction < 0 && articleRect.height > window.innerHeight) {