D&D v2 message editor enhancement: modules, timer and message preview

We are equipping the editor with new options and improving those that were already available:

• We’ve added a Timer block, allowing you to add countdowns into your content.
• You can now conveniently preview your newsletter creation. With a single click, you can see how your designed message will appear on both mobile phones and computers.
• The D&D v2 editor is now accessible within newly created business units.
• Modules containing images will now save correctly, ensuring that graphics are included as intended.