Create the 'About content' widget

There should be an aboutcontent widget that has 2 different tabs. The first tab is the Details tab and shows the metadata of the content (title, description, url, created by). When a description is not available, it should not be shown. The second tab is the Shared with tab and shows the list of members of the content.
Maybe it would be better to assert that the total button count is the same as the asserts we've already done. That would avoid a scenario where a button different than `Details` and `Shared with` wouldn't be picked up