Implement divide functionality for Vec2, Vec3 and Vec4 classes

[mvaligursky]

Currently we have:

• mul - multiplies vector by vector
• scale - multiplies vector by scalar

We should consider similar functionality for divide operation.

[willeastcott]

How about if the API was like this:

Vec3#mulScalar(n: number) : Vec3
Vec3#mul(vec: Vec3) : Vec3
Vec3#mul2(vec1: Vec3, vec2: Vec3) : Vec3

Vec3#divScalar(n: number) : Vec3
Vec3#div(vec: Vec3) : Vec3
Vec3#div2(vec1: Vec3, vec2: Vec3) : Vec3

Vec3#addScalar(n: number) : Vec3
Vec3#add(vec: Vec3) : Vec3
Vec3#add2(vec1: Vec3, vec2: Vec3) : Vec3

Vec3#subScalar(n: number) : Vec3
Vec3#sub(vec: Vec3) : Vec3
Vec3#sub2(vec1: Vec3, vec2: Vec3) : Vec3

And we deprecated Vec3#scale.

And same for Vec2 and Vec4 of course.

[mvaligursky]

sounds good but not sure we need these, it's not common to do that:

Vec3#addScalar(n: number) : Vec3
Vec3#subScalar(n: number) : Vec3

Maybe we should add these:

Vec3#mulScalar2(n: number, vec: Vec3)
Vec3#divScalar2(n: number, vec: Vec3)

[Maksims]

Won't it become many ways of doing the same thing?
.scale - is very common across all various math libs and languages. .scale(1/s) is same as .div(s).
Although "div" is conflicting name in the web with DOM div.

For readability of code, I rarely see Devs using mul2.

[willeastcott]

@Maksims This issue originated from here: https://forum.playcanvas.com/t/dividing-vectors/18583/6

The problem is that, for you or I, it's obvious that div(x) is scale(1/x). But to some developers, it's just not obvious, or even intuitive if you are using autocomplete in the code editor. It seems reasonable that a lot of developers will think "I want to divide this vector" and start typing vec.div to bring up autocomplete (only to find it doesn't exist). I think we're just used to the current API.