[BridgeJS] Generated `JSTypedClosure` initializer is always internal

[sliemeobn]

I have a type like this in a target:

@JSClass(jsName: "Document")
public struct JSDocument {
     // ...
    @JSFunction public func addEventListener(_ type: String, _ listener: JSTypedClosure<(JSEvent) -> Void>) throws(JSException)
    @JSFunction public func removeEventListener(_ type: String, _ listener: JSTypedClosure<(JSEvent) -> Void>) throws(JSException)
}

unfortunately, I cannot directly initialize a JSTypedClosure<(JSEvent) -> Void> in another target, because the generated init is internal.

not sure how to best solve this, but currently you'll need to manually add some public/package function to actually be able to make such a closure.

[kateinoigakukun]

I think we can make the synthesized initializers public when the closure appears in public surfaces