Add `ImmutableVector3Builder`

[ink0rr]

It's mentioned in a comment, but the implementation doesn't exists.

minecraft-scripting-libraries/libraries/math/src/vector3/vectorWrapper.ts

Line 13 in 8cf3f6a

* For an immutable version of the build, use ImmutableVector3Builder.

[rlandav]

A build of a stale comment leftover when I was first implementing this I guess. I was a bit torn on how valuable people would find the immutable version vs. just using the functions instead. Is this something you would find valuable?

[ink0rr]

Not really, I've settled with just cloning the vector when I need to avoid mutating the original object.

const a = new Vector3Builder(0, 0, 0);
const b = new Vector3Builder(a).add({ x: 1, y: 2, z: 3 });

Though it looks kinda awkward, I think it would be nice to have something like a .clone() method if possible.

const a = new Vector3Builder(0, 0, 0);
const b = a.clone().add({ x: 1, y: 2, z: 3 });