toolbar.items.templateString|Function
Specifies what element will be added in the ToolBar wrapper. Items with template does not have a type.
Example
<div id="taskBoard"></div>
<script>
$("#taskBoard").kendoTaskBoard({
    toolbar: {
        items: [
            { 
                template: (data) => `<button class="k-button"><span class="k-icon k-i-star"></span>Custom Template</button>`
            },
            { text: "Regular Button", icon: "gear" }
        ]
    },
    dataSource: [
        { id: 1, title: "Task 1", status: "todo" }
    ],
    columns: [
        { text: "To Do", status: "todo" }
    ]
});
</script>
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