Custom Toolbar Items can be inserted to the Toolbar by using an object in the format:

• name - denotes the name of the item, which can be used as a reference for CSS and JS selectors
• content - the HTML content of the item
• init - callback function that is called when the item is initialized
• action - callback function that is called when the item is clicked

The demo featues a custom toolbar item for quickly switching the chart's type between 'column' and 'line'