Function handleSave

examples/tutorial/src/components/TopBar.js:16–21

()

        loadTree
    } = builder;
    const handleSave = () => {
        // Maybe let save your work 
        // to a storage service? 
        // Or a database? A file...?
        console.log(json());
    }
    return <div>
        <button onClick = {handleSave}>
            Save