Add look rotation example

[aglitchman]

The point of the example is to show how to use Defold API to write your own math function. The math function is look rotation, that is used in probably 95% of the 3D examples for the Unity engine. Obviously, when a person comes to Defold, they may have knowledge from Unity / Godot, and will look for familiar functions in Defold.

• https://docs.godotengine.org/en/stable/classes/class_basis.html#class-basis-method-looking-at
• https://docs.unity3d.com/ScriptReference/Quaternion.LookRotation.html

In this demo you can rotate the camera by holding down the mouse button. And also switch "targets" by pressing any key.