Variadic function arguments

[nrigaudiere]

Let's say a JS function must accept a variadic arguments of Node as input, ...nodes.

We have 2 solutions to handle this on the native API:

1. use the built-in slice, ie. []Node
2. use a custom generated type, VariadicNodes generated through a provided helper function Variadic(comptime T: type) type

The slice solution is easier to use as you don't have to generate the Variadic<Type>. But it's also less explicit and can lead to some misunderstanding:

• it's not a JS Array as the semantics might make you think (see Handle JS Array #52)
• the Native -> JS translation will not be possible, therefore returning []Node will be forbidden, which is less obvious than forbid to return a VariadicNode