Sets or gets the tab index of an element on a site page.
The tabIndex property determines the order in which elements can be focused on or selected using the tab key on the keyboard. By default, web browsers only assign a tab index to interactive elements such as links and form controls. When set to 0, the element becomes part of the keyboard tab and focus order. When set to -1, the element isn't part of the keyboard focus order but can still become focusable using the focus() function.
Supported values: -1, 0