Transform.xform() and Transform.xform_inv() methods are missing

[Bauxitedev]

In Godot, you can call Transform.xform(v) to apply the transform to v (where v can be a vector, plane, AABB or vector array), and xform_inv to apply the inverse transform. See https://docs.godotengine.org/en/stable/classes/class_transform.html#class-transform-method-xform

This method appears to be missing in the gdnative bindings: https://docs.rs/gdnative/0.9.3/gdnative/core_types/struct.Transform.html

[Waridley]

Related: #290

[Demindiro]

For the xform function a trait with Mul as supertrait could be used, e.g.:

// mod.rs
pub trait XForm<T>: Mul<T> {
	fn xform(&self, with: T) -> Self::Output
	where
		Self: Sized
	{
		self * with
	}
}

// transform.rs
impl XForm<Vector3> for Transform {}

That way xform can also be used for multiple types without suffixing a type to it (e.g. xform_vector3), if that's desired.