Add In-World UI example #5479

What problem does this solve or what need does it fill?

When #5476 is solved, we need example(s) showcasing how to setup and use UI in-world.

What solution would you like?

Examples showcasing the following features:

• How to display UI in the world
• Display multiple separate UI elements in the world
• How to interact with in-world UI

These can be one and the same example, or multiple depending on how big they need to be in order to showcase what they need. Just showing a couple of different UI elements that isn't 100% camera-facing with buttons that can be pressed should be enough to showcase what we need, but feel free to come up with something more interesting.