Interface for a class HeaderRows
It defines the header row type, which accepts either of the following values.
Year: Denotes the year row in the header bar.
Month: Denotes the month row in the header bar.
Week: Denotes the week row in the header bar.
Date: Denotes the date row in the header bar.
Hour: Denotes the hour row in the header bar.
Template option to customize the individual header rows. It accepts either the string or HTMLElement as template design
content and parse it appropriately before displaying it onto the header cells. The field that
can be accessed via this template is