Can we add a class to the admin tabs?

Description of the need I was looking at styling the tabs slightly differently and realized they don't have any identifying classes (e.g. the "Edit" tab does not have an "edit" class) so are hard to pinpoint precisely with CSS.

Recommended solution Add a view class to the View tab and an edit class to the Edit tab.

PR: https://github.com/backdrop/backdrop/pull/3320