quaternion multiply operator not documented

[seocwen]

https://docs.godotengine.org/en/3.2/classes/class_quat.html

The quat class is missing documentation of the * operator, which is strange because this is the most important thing that quaternion's do. There isn't a * or *= on the whole page.

[Calinou]

Most built-in classes like Vector2/Vector3/Color also don't have their supported operators documented explicitly. We should probably address this for all classes at once.

[jynus]

This was fixed in godotengine/godot#43419, although not sure it was backported- or at least, docs for stable versions (including the one sent above) weren't regenerated, if it was. The "latest" version has the operators, though: https://docs.godotengine.org/en/latest/classes/class_quaternion.html

[Vennnot]

We need a GD 3.x doc tag in order to be able to label this issue correctly.