Add tab bar and tab pane

[dhardy]

See this comment and follow-ups.

To recap: the "tab pattern" is comprized of a TabList and one or more TabPanels. Typically only one TabPanel will be shown at a time. The TabList contain one ore more Tabs, each corresponding to a TabPanel. The Tabs support the selection state.

Originally posted by @DataTriny in #521 (comment)

Related: #524