add quiz universal plugin feature flag

closes CNVS-19377

test plan:
 - verify that there is a new feature flag named "Quiz LTI plugin"
   that must be allowed from the root account, but can be switched
   on or off on the course

Change-Id: I42870d920f93667ef9f147a64b0e06990d5f3b90
Reviewed-on: https://gerrit.instructure.com/50592
Tested-by: Jenkins
Reviewed-by: Ryan Taylor <rtaylor@instructure.com>
QA-Review: Robert Lamb <rlamb@instructure.com>
Product-Review: Hilary Scharton <hilary@instructure.com>

lib/feature.rb

@@ -308,6 +308,15 @@ END
         applies_to: 'RootAccount',
         state: 'hidden',
         beta: true
+      },
+    'quizzes_lti' =>
+      {
+        display_name: -> { I18n.t('Quiz LTI plugin') },
+        description: -> { I18n.t('Use the new quiz LTI tool in place of regular canvas quizzes') },
+        applies_to: 'Course',
+        state: 'hidden',
+        beta: true,
+        root_opt_in: true
       }
   )