FEATURE: add a delay on the "mention" warning in composer

Previously we would warn too early about lack of visibility

app/assets/javascripts/discourse/components/composer-editor.js.es6

@@ -425,8 +425,16 @@ export default Ember.Component.extend({
         let name = $e.data('name');
 
         if (found.indexOf(name) === -1) {
-          this.sendAction('cannotSeeMention', [{ name: name }]);
+
-          found.push(name);
+          // add a delay to allow for typing, so you don't open the warning right away
+          // previously we would warn after @bob even if you were about to mention @bob2
+          Em.run.later(this, () => {
+            if ($preview.find('.mention.cannot-see[data-name="' + name + '"]').length > 0) {
+              this.sendAction('cannotSeeMention', [{ name: name }]);
+              found.push(name);
+            }
+          }, 2000);
+
         }
       });