[Innovation] Onboarding: Tours & Hints

[juanfra]

🎫 Ticket

N/A

🗒️ Description

• Adding an example tour, based on the work of https://github.com/the-events-calendar/tribe-common/pull/1574
• Extending abstract class, adding tour steps and CSS classes.

🎥 Artifacts

✔️ Checklist

• [ ] I've included a readme.txt Changelog entry.
• [ ] My code is tested.
• [ ] My code has proper inline documentation.