Added TK reminders labs feature (#19057)

refs TryGhost/Product#4156

apps/admin-x-settings/src/components/settings/advanced/labs/AlphaFeatures.tsx

@@ -59,6 +59,10 @@ const features = [{
     title: 'AdminX Demo',
     description: 'Adds a navigation link to the AdminX demo app',
     flag: 'adminXDemo'
+},{
+    title: 'TK Reminders',
+    description: 'Enables the TK Reminders feature in the editor',
+    flag: 'tkReminders'
 }];
 
 const AlphaFeatures: React.FC = () => {

ghost/core/core/shared/labs.js

@@ -48,7 +48,8 @@ const ALPHA_FEATURES = [
     'editorEmojiPicker',
     'adminXOffers',
     'filterEmailDisabled',
-    'adminXDemo'
+    'adminXDemo',
+    'tkReminders'
 ];
 
 module.exports.GA_KEYS = [...GA_FEATURES];