[Tabs] Missing width/height state in Tabs.Indicator render callback

[aarongarciah]

Feature request

Summary

The Tabs.Indicator element exposes the following CSS vars in order to let users style/animate the element:

--active-tab-top
--active-tab-right
--active-tab-bottom
--active-tab-left

--active-tab-width
--active-tab-height

The state argument in the render callback of the Tabs.Indicator component includes a selectedTabPosition object which contains {top, right, bottom , left}. These coordinates correspond to the first four CSS vars, but --active-tab-width and --active-tab-height have no corresponding state keys.

Motivation

Some users might need to access the width/height of the selected tab in JS. For example, it's useful if someone is relying on Motion to animate the tabs indicator. See this example: https://codesandbox.io/p/sandbox/black-platform-4zphr8?workspaceId=ws_HE9JRzFW36Y2kpBoSwdvZ5. The coordinates of the tabs indicator can be animated using Motion but not the width because width/height is not exposed in the render callback state.

Further context: https://discord.com/channels/1287292451308048406/1287292451308048409/1325583630956888135