Isolate dispose cause the memory leak

[wwsheng009]

Isolate dispose cause the memory leak。

https://github.com/rogchap/v8go/blob/cee5f84bb54338bdef150b3e43daace4669c5de2/isolate.go#L147C1-L147C1

func (i *Isolate) Dispose() {
	if i.ptr == nil {
		return
	}
	C.IsolateDispose(i.ptr)
	i.ptr = nil
	i.cbs = nil //shoud release the cbs,otherwise the memory will leak。
}