Add Tabs example that supports Reflow regardless of number of tabs

[mcking65]

In discussion of #2284, we concluded that we need an example that shows how to implement a tabbed interface that supports WCAG 1.4.10 reflow requirements as the number of tabs grows beyond what can fit within viewport width when zoomed. To avoid adding substantial complexity to the basic tabs example, we decided to illustrate this feature in a separate example.

One common approach is an overflow menu that lists the tabs that are not shown. Choosing an option in the menu replaces the right-most tab with the chosen tab and then activates the chosen tab. The tab that was previously visible as the right most tab would be added to the overflow menu.