The changelog can also be viewed at News in 3.14 | SuperCollider 3.14.0 Help
Work on 3.15.0 has already started and it will offer some really great new features - we hope to get it out sooner than later 
Regarding themed docs: If you want to change the theme of the docs you have to do this via the docs itself. For this the navbar needs to have enough space in order to display the theme dropdown menu, see
No theme dropdown menu b/c the docs dock is not wide enough
Increase width and it becomes visible
Click on the desired theme - this will not be automatically synced with the theme of the IDE!
With version 3.14.0 it is also possible to “snap-zoom” within IDE documents on macOS, just like in a browser