support dark mode in Tabs

[sgratzl]

e.g. the Button component supports a dark variant but he Tabs one does not.

[craigkovatch]

I will pass on this request to our visual designer, but just to be forthcoming I would not expect this on a short timeline.

[craigkovatch]

@sgratzl v3.14 now supports Dark Mode for ~all components. The dark variant you previously mentioned for Button was really an "inverse" variant, i.e. meant to be used on a dark-colored container.

Please note that dark mode is not yet automatically switched, but it can be manually enabled by adding CSS class tds-dark to the document root element (i.e. html element or in JS document.documentElement)