Create the 'About discussion' widget

There should be an aboutdiscussion widget that has 2 different tabs. The first tab is the Details tab and shows the metadata of the discussion (title, description, 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 discussion.
I've wrapped this in a `aboutcontent-created` div in the other PR. Can you do the same here and apply the font size to that?