isNode
import { isNode } from "https://github.gh-proxy.cn/raw.githubusercontent.com/baetheus/fun/main/free.ts";Check if a Free structure is a Node.
@example
import { isNode, node, link } from "./free.ts";
const single = node(1);
const combined = link(node(1), node(2));
console.log(isNode(single)); // true
console.log(isNode(combined)); // false